CN104183834A - Preparation method of sulphur/silicon dioxide core-shell nanostructure for lithium sulphur battery anode - Google Patents

Abstract

The invention relates to a preparation method of a sulphur/silicon dioxide core-shell nanostructure for a lithium sulphur battery anode. The preparation method comprises the following steps: dispersing a surface active agent in sulfuric acid solution, dropwise adding sodium thiosulfate aqueous solution, stirring for 0.5-24h, washing products, and drying to obtain sulphur particles; and dispersing the sulphur particles and the surface active agent in ethanol solution, sequentially adding water, ammonia water and tetraethoxysilane solution, reacting for 0.5-12h at room temperature, washing products and drying to obtain the sulphur/silicon dioxide core-shell nanostructure. According to the preparation method, the sulphur particle is used as a template, nano-porous silicon dioxide is clad by a hydrolytic polycondensation process of tetraethoxysilane, the loss of the active substance in an electrode process can be effectively inhibited, and the cycling stability and the rate capability of the electrode are improved under the immobilization and catalytic action of the nano-porous silicon dioxide on the sulphur active substance, therefore, the high-performance composite anode material is obtained.

Description

A preparation method of sulfur/silicon dioxide core-shell nanostructure for positive electrode of lithium-sulfur battery

technical field

The invention relates to a preparation method of a sulfur positive electrode material for a lithium-sulfur battery, in particular to a preparation method of a sulfur/silicon dioxide core-shell nanostructure for a lithium-sulfur battery positive electrode. the

Background technique

Lithium-ion secondary batteries that are increasingly commercialized are limited by their theoretical capacity, and their energy density cannot be further significantly increased. Fuel cells are also difficult to be practical in a short period of time, and the current technology is far from meeting the needs of development. Therefore, there is an urgent need to research and develop new chemical power sources with higher energy density, longer cycle life, low cost, and environmental friendliness.

Lithium-sulfur secondary batteries (referred to as lithium-sulfur batteries), which use metallic lithium as the negative electrode and elemental sulfur as the positive electrode active material, have received widespread attention due to their high theoretical capacity, wide source of raw materials, low price, and environmental friendliness. It is the most potential candidate for the next generation energy storage system. However, the dissolution of polysulfides produced by the sulfur electrode itself during the discharge process and the resulting shuttle effect directly lead to the reduction of the utilization rate of active materials, the poor cycle stability of the electrode and the poor performance of high-rate charge and discharge. Meeting the requirements of transportation and energy storage power batteries restricts the practical application of lithium-sulfur batteries.

In recent years, people have improved the performance of sulfur electrodes mainly by constructing sulfur-based composite materials, using composite supports such as amorphous carbon, carbon nanotubes and conductive polymers. Compared with these carbon-based supports, nanoporous oxides such as silica, titania, and alumina as supports can not only immobilize sulfur active species, but also catalyze the electrode process, thus inhibiting the electrode process more effectively. The loss of active material during the process improves the cycle stability and rate performance of the electrode, and obtains a high-performance composite sulfur cathode material. Among these oxide supports, silica has attracted much attention due to its advantages of facile preparation, low cost, and environmental friendliness. However, the existing methods of silica addition are difficult to achieve uniform mixing with the active substance sulfur, and the preparation of nanoporous silica loaded or coated with sulfur, especially the sulfur/silica core-shell nanostructure still faces great challenges. challenges, which limit the access to high-performance composite sulfur cathode materials through nanoporous silica modification.

The present invention aims to seek a method for preparing sulfur/silicon dioxide core-shell nanostructures. the

Contents of the invention

The object of the present invention is to provide a method for preparing a sulfur/silicon dioxide core-shell nanostructure for the positive electrode of a lithium-sulfur battery.

A method for preparing a sulfur/silicon dioxide core-shell nanostructure for a positive electrode of a lithium-sulfur battery, comprising the following steps:

(1) Preparation of sulfur granules: Disperse the surfactant in sulfuric acid solution, add dropwise an aqueous solution of sodium thiosulfate, stir for 0.5 to 24 hours, wash and dry the product, and obtain the sulfur granule product;

(2) Preparation of sulfur/silica core-shell nanostructure: Disperse the sulfur particles and surfactant obtained in step (1) into an ethanol solution, then add water, ammonia water and tetraethyl orthosilicate solution in sequence, and react at room temperature After 0.5-12 hours, the product is washed and dried to obtain the sulfur/silicon dioxide core-shell nanostructure.

In step (1), the surfactant is one of polyvinylpyrrolidone, cetyltrimethylammonium bromide, polydiallyldimethylammonium chloride, sodium polystyrene sulfonate or several kinds; the mass concentration of the surfactant is 1-100 g/L; the concentration _of the sulfuric acid solution is 0.1-100 mmol/L; the molar ratio of the sodium thiosulfate to _H2SO4 is 1 ~100:1.

In step (2), the concentration of the sulfur particles in the ethanol solution is 0.01 to 10 grams per liter; the surfactant is polyvinylpyrrolidone, cetyltrimethylammonium bromide, polydiallyl One or more of dimethyl ammonium chloride and sodium polystyrene sulfonate; the mass concentration of the surfactant is 0.1 to 10 grams per liter;

In the present invention, the mass percentage of _NH3 in the ammonia water is 25-28%, and the mass percentage of _SiO2 in the tetraethylorthosilicate solution is higher than 28.0%. The volume ratio of the ethanol solution, water, ammonia water and tetraethyl orthosilicate solution is 1:0.1-0.5:0.1-0.5:0.00005-0.001.

In the present invention, the range of room temperature is 0~40 ^o C.

The present invention has the following beneficial technical effects:

(1) The present invention uses nanoporous silica as a carrier to coat sulfur particles. The nanoporous silica carrier can not only fix sulfur active substances, but also catalyze the electrode process, so it can effectively inhibit the electrode process. The loss of the active material improves the cycle stability and rate performance of the electrode, and obtains a high-performance composite sulfur cathode material.

(2) The present invention uses sulfur particles as a template, and adopts the hydrolysis and polycondensation process of ethyl orthosilicate to coat nanoporous silica, which overcomes the difficulty in the preparation of sulfur/silica core-shell nanostructures; the preparation method is simple and environmentally friendly. Friendly, can achieve large-scale production.

(3) The present invention can adjust the size of sulfur particles, the thickness of nanoporous silica layer and the ratio of silica to sulfur by controlling the reaction time, the concentration and ratio of reaction raw materials, and further regulate the lithium storage capacity of the composite material system performance.

Description of drawings

Figure 1: X-ray diffraction patterns of sulfur particles and sulfur/silica core-shell nanostructures prepared in Example 1.

Figure 2: Transmission electron micrograph of the sulfur particles prepared in Example 1.

Fig. 3: The energy spectrum of the sulfur/silica core-shell nanostructure prepared in Example 1.

Figure 4: Transmission electron micrograph of the sulfur/silica core-shell nanostructure prepared in Example 1.

Fig. 5: High-resolution transmission electron micrograph of the sulfur/silica core-shell nanostructure prepared in Example 1.

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Detailed ways

The present invention will be described in detail below in conjunction with specific embodiments. The protection scope of the present invention is not limited by the specific embodiments, but by the claims.

the

Example 1:

A method for preparing a sulfur/silicon dioxide core-shell nanostructure for a positive electrode of a lithium-sulfur battery, the steps are as follows:

(1) Preparation of sulfur particles: disperse 5 grams of polyvinylpyrrolidone into 500 milliliters of 3 mmol/liter sulfuric acid solution, add dropwise 50 milliliters of 0.3 moles/liter sodium thiosulfate aqueous solution, stir for 2 hours, and dissolve the product Washing and drying to obtain sulfur granular product;

(2) Sulfur/silica core-shell nanostructure: disperse 0.1 gram of sulfur particles obtained in step (1) and 80 mg of cetyltrimethylammonium bromide into 60 milliliters of ethanol solution, and then add 15 Milliliter water, 0.75 milliliter ammonia water and 0.15 milliliter tetraethyl orthosilicate solution were reacted at room temperature for 1 hour, and the product was washed and dried to obtain the sulfur/silica core-shell nanostructure.

FIG. 1 is an X-ray diffraction pattern of sulfur particles and sulfur/silica core-shell nanostructures synthesized in Example 1. It can be seen from the figure that the crystalline phase of the sulfur/silica core-shell nanostructure is consistent with the crystalline phase of the sulfur particles, both of which are orthorhombic sulfur (JCPDS 08-0247), while the silica shell is in an amorphous state . Figure 2 is a transmission electron micrograph of the sulfur particles synthesized in this example. It can be seen from the figure that the morphology of the prepared sulfur is basically spherical, and the size distribution of the spherical particles is relatively uniform. Fig. 3 is an energy spectrum diagram of the sulfur/silica core-shell nanostructure synthesized in this example. It can be seen from the figure that the elemental peaks of sulfur come from the core of the sulfur particle in the core-shell nanostructure, while the elemental peaks of silicon and oxygen come from the silica shell of the core-shell nanostructure. Fig. 4 and Fig. 5 are transmission electron micrographs and high-resolution transmission electron micrographs of the sulfur/silica core-shell nanostructure synthesized in this example, respectively. It can be seen from the figure that the product shows a typical core-shell structure, and the surface of the sulfur particle core is covered with a uniform nanoporous silica shell. The nanoporous silica carrier can not only immobilize sulfur active substances, but also catalyze the electrode process, so it can effectively inhibit the loss of active substances in the electrode process, improve the cycle stability and rate performance of the electrode, and is conducive to obtaining high Performance composite sulfur cathode material.

the

Example 2:

A method for preparing a sulfur/silicon dioxide core-shell nanostructure for a positive electrode of a lithium-sulfur battery, the steps are as follows:

(1) Preparation of sulfur particles: Disperse 1 gram of polyvinylpyrrolidone into 1 liter of 0.1 mmol/L sulfuric acid solution, add dropwise 25 mL of 4 mmol/L sodium thiosulfate aqueous solution, stir for 0.5 hour, and The product is washed and dried to obtain a sulfur particulate product;

(2) Sulfur/silica core-shell nanostructure: disperse 0.3 mg of sulfur particles and 3 mg of cetyltrimethylammonium bromide obtained in step (1) into 30 ml of ethanol solution, then add 3 Milliliter water, 3 milliliter ammonia water and 1.5 microliter tetraethyl orthosilicate solution were reacted at room temperature for 0.5 hour, and the product was washed and dried to obtain the sulfur/silica core-shell nanostructure. The result is similar to Example 1.

the

Example 3:

A method for preparing a sulfur/silicon dioxide core-shell nanostructure for a positive electrode of a lithium-sulfur battery, the steps are as follows:

(1) Preparation of sulfur particles: disperse 100 grams of polyvinylpyrrolidone into 1 liter of 100 mmol/liter sulfuric acid solution, add dropwise 250 milliliters of 40 mol/liter sodium thiosulfate aqueous solution, stir for 24 hours, and dissolve the product Washing and drying to obtain sulfur granular product;

(2) Sulfur/silica core-shell nanostructure: Disperse 1.2 g of sulfur particles and 1.2 mg of polyvinylpyrrolidone obtained in step (1) into 120 ml of ethanol solution, then add 60 ml of water, 60 ml of ammonia and 0.12 ml tetraethyl orthosilicate solution was reacted at room temperature for 12 hours, and the product was washed and dried to obtain the sulfur/silicon dioxide core-shell nanostructure. The result is similar to Example 1.

the

Example 4:

A method for preparing a sulfur/silicon dioxide core-shell nanostructure for a positive electrode of a lithium-sulfur battery, the steps are as follows:

(1) Preparation of sulfur particles: disperse 60 grams of polydiallyldimethylammonium chloride into 1 liter of 18 mmol/liter sulfuric acid solution, add dropwise 500 milliliters of 2 mol/liter sodium thiosulfate aqueous solution, stirred for 15 hours, and the product was washed and dried to obtain a sulfur granular product;

(2) Sulfur/silica core-shell nanostructure: disperse 0.3 g of sulfur particles and 0.3 g of sodium polystyrene sulfonate obtained in step (1) into 60 ml of ethanol solution, then add 18 ml of water, 18 Milliliter ammonia water and 0.03 milliliter tetraethyl orthosilicate solution were reacted at room temperature for 45 minutes, and the product was washed and dried to obtain the sulfur/silica core-shell nanostructure. The result is similar to Example 1.

the

Example 5:

A method for preparing a sulfur/silicon dioxide core-shell nanostructure for a positive electrode of a lithium-sulfur battery, the steps are as follows:

(1) Preparation of sulfur particles: Disperse 5 g of sodium polystyrene sulfonate into 1 liter of 2 mmol/L sulfuric acid solution, add dropwise 120 mL of 0.1 mol/L sodium thiosulfate aqueous solution, and stir for 1 hour , the product is washed and dried to obtain a sulfur particle product;

(2) Sulfur/silica core-shell nanostructure: Disperse 2.4 mg of sulfur particles and 15 mg of polydiallyldimethylammonium chloride obtained in step (1) into 30 ml of ethanol solution, and then add 4.5 milliliters of water, 4.5 milliliters of ammonia water and 80 microliters of tetraethyl orthosilicate solution were reacted at room temperature for 6 hours, and the product was washed and dried to obtain the sulfur/silica core-shell nanostructure. The result is similar to Example 1. the

Claims (7)

1. A method for preparing a lithium-sulfur battery positive electrode sulfur/silicon dioxide core-shell nanostructure, characterized in that, comprising the following steps: (1) Preparation of sulfur granules: Disperse the surfactant in sulfuric acid solution, add dropwise an aqueous solution of sodium thiosulfate, stir for 0.5 to 24 hours, wash and dry the product, and obtain the sulfur granule product; (2) Preparation of sulfur/silica core-shell nanostructure: Disperse the sulfur particles and surfactant obtained in step (1) into an ethanol solution, then add water, ammonia water and tetraethyl orthosilicate solution in sequence, and react at room temperature After 0.5-12 hours, the product is washed and dried to obtain the sulfur/silicon dioxide core-shell nanostructure. 2. The preparation method of sulfur/silicon dioxide core-shell nanostructure for lithium-sulfur battery anode according to claim 1, characterized in that: in step (1), the surfactant is polyvinylpyrrolidone, hexadecane One or more of trimethylammonium bromide, polydiallyldimethylammonium chloride, and sodium polystyrene sulfonate; the mass concentration of the surfactant is 1 to 100 grams per liter. 3. The preparation method of sulfur/silicon dioxide core-shell nanostructures for lithium-sulfur battery positive electrodes according to claim 1, characterized in that: in step (1), the concentration of the sulfuric acid solution is 0.1 to 100 mmol/ liter; the molar ratio of sodium thiosulfate to H ₂ SO ₄ is 1 to 100:1. 4. The method for preparing a sulfur/silicon dioxide core-shell nanostructure for lithium-sulfur battery positive electrode according to claim 1, characterized in that: in step (2), the concentration of the sulfur particles in the ethanol solution is 0.01~ 10 g/l. 5. The preparation method of sulfur/silicon dioxide core-shell nanostructure for lithium-sulfur battery cathode according to claim 1, characterized in that: in step (2), the surfactant is polyvinylpyrrolidone, hexadecane One or more of trimethylammonium bromide, polydiallyldimethylammonium chloride, and sodium polystyrene sulfonate; the mass concentration of the surfactant is 0.1 to 10 grams per liter. 6. The preparation method of the sulfur/silicon dioxide core-shell nanostructure for lithium-sulfur battery anode according to claim 1, characterized in that: in step (2), the ethanol solution, water, ammonia and ethyl orthosilicate The volume ratio of the solution is 1:0.1~0.5:0.1~0.5:0.00005~0.001. 7. The preparation method of sulfur/silicon dioxide core-shell nanostructure for lithium-sulfur battery cathode according to claim 1, characterized in that: in step (2), the mass percentage of NH in the ammonia water is ₂₅ ~28%, the mass percentage of _SiO2 in the tetraethyl orthosilicate solution is higher than 28.0%.