WO2017139990A1

WO2017139990A1 - Method for preparing alumina-hollow-sphere cathode material for lithium-sulfur battery

Info

Publication number: WO2017139990A1
Application number: PCT/CN2016/074186
Authority: WO
Inventors: 肖丽芳; 钟玲珑
Original assignee: 肖丽芳
Priority date: 2016-02-21
Filing date: 2016-02-21
Publication date: 2017-08-24

Abstract

Provided in the invention is a method for preparing an alumina-hollow-sphere cathode material for a lithium-sulfur battery, the method comprising the following steps: step (1), dispersing aluminum powder in an aqueous solution of aluminum silicate octadecahydrate, stirring, thereafter gradually adding urea thereto and continuing stirring until precipitate no longer increases, and after the complete reaction, filtering the precipitate, washing same with water and drying same so as to obtain an Al-Al(OH)₃ material; step (2), putting the obtained Al-Al(OH)₃ material into a muffle furnace for high-temperature calcination, to obtain hollow aluminum oxide spheres after the complete reaction; and step (3) adding the obtained hollow aluminum oxide spheres, elemental sulfur and graphene into carbon disulfide for ultrasonic dispersion to form a suspension, and then evaporating the solvent, so as to obtain a composite material. In the graphene/aluminum oxide hollow sphere/sulfur composite material, the aluminum oxide hollow spheres coat the sulfur-based material, suppressing the dissolution of the discharge product, polysulfide, and reducing volume expansion, improving the electrochemical properties thereof.

Description

Preparation method of alumina hollow sphere lithium sulfur battery cathode material

Technical field

The invention relates to the synthesis of nano materials, in particular to a method for preparing a cathode material of a lithium sulfur battery.

Background technique

The lithium-sulfur battery is a battery system in which lithium metal is used as a negative electrode and elemental sulfur is used as a positive electrode. Lithium-sulfur batteries have two discharge platforms (about 2.4V and 2.1V), but their electrochemical reaction mechanism is complicated. Lithium-sulfur batteries have the advantages of high specific energy (2600Wh/kg), high specific capacity (1675mAh/g), low cost, etc., and are considered to be promising new generation batteries. However, at present, there are problems such as low utilization rate of active materials, low cycle life and poor safety, which seriously restricts the development of lithium-sulfur batteries. The main causes of the above problems are as follows: (1) Elemental sulfur is an electron and ion insulator, and the room temperature conductivity is low (5 × 10 ^-30 S·cm ^-1 ). Since there is no ionic sulfur, it is used as The activation of the positive electrode material is difficult; (2) the high polylithium polysulfide Li ₂ S _n (8>n≥4) generated during the electrode reaction is easily dissolved in the electrolyte, forming a concentration difference between the positive and negative electrodes. Under the action of the concentration gradient, it migrates to the negative electrode, and the high poly lithium polysulfide is reduced by the lithium metal to the oligomeric lithium polysulfide. As the above reaction proceeds, the oligomeric lithium polysulfide aggregates at the negative electrode, eventually forming a concentration difference between the two electrodes, and then migrating to the positive electrode to be oxidized to a highly polylithium polysulfide. This phenomenon is known as the shuttle effect, which reduces the utilization of sulfur active substances. At the same time, insoluble Li ₂ S and Li ₂ S _{2 are} deposited on the surface of the lithium negative electrode, which further deteriorates the performance of the lithium-sulfur battery; (3) the final product of the reaction, Li ₂ S, is also an electronic insulator, which is deposited on the sulfur electrode, and lithium The migration speed of ions in solid lithium sulfide is slow, which makes the electrochemical reaction kinetics slower. (4) The density of sulfur and the final product Li ₂ S is different. When the sulfur is lithiated, the volume expands by about 79%, which easily leads to Li _{2 .} The powdering of S causes safety problems in lithium-sulfur batteries. The above-mentioned shortcomings restrict the development of lithium-sulfur batteries, which is also the key issue that needs to be solved in the research of lithium-sulfur batteries.

technical problem

The technical problem to be solved by the present invention is to provide a graphene/alumina hollow sphere/sulfur composite material, which has a simple preparation method, a conductive conductive graphene provides a conductive network, and a hollow structure alumina coated with a sulfur-based material, capable of Prevents the dissolution of polysulfide in the discharge product and relieves volume expansion, improving the electrochemical properties of the material performance.

Problem solution

Technical solution

The invention provides a preparation process of a graphene/alumina hollow sphere/sulfur composite material as follows:

(1) Disperse the aluminum powder in an aqueous solution of 18-aqueous aluminum silicate, stir, and then gradually add urea to continue stirring until the precipitation does not increase. After the reaction is completed, the precipitate is filtered, washed with water, and dried at 60 ° C to obtain Al- Al(OH) ₃ material.

(2) The obtained Al-Al(OH) ₃ material was placed in a muffle furnace for high-temperature calcination, and after completion of the reaction, hollow alumina was obtained.

(3) The obtained hollow alumina, sulfur elemental, and graphene are added to carbon disulfide, ultrasonically dispersed to form a suspension, and then the solvent is evaporated to obtain a composite material.

The particle size of the aluminum powder in step (1) is 1-100 um, and the concentration of the aqueous solution of octahydrate aluminum silicate is 0.2-0.4 mol/L;

The temperature of the high temperature calcination in the step (2) is 900-1100 ° C, and the reaction time is 1-3 hours;

Step (3) The mass ratio of hollow alumina, sulfur elemental, graphene is 15-30:60-80:5-10; the ultrasonic dispersion time is 0.5-5 hours; and the temperature of the evaporated solvent is 40-60 °C.

Advantageous effects of the invention

Beneficial effect

The invention has the following beneficial effects: (1) graphene has ultra-high electrical conductivity, and the graphene/alumina hollow sphere/sulfur composite material prepared by the method can effectively improve the electronic conductivity of the cathode material of the lithium-sulfur battery and Ionic conductivity; (2) Graphene/alumina hollow sphere/sulfur composite material coated with sulfur-based material in alumina hollow sphere, can inhibit the dissolution of polysulfide of discharge products and relieve volume expansion, improve its electrochemical performance .

Brief description of the drawing

DRAWINGS

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an SEM image of a graphene/alumina hollow sphere/sulfur composite prepared in accordance with the present invention.

Invention embodiment

Embodiments of the invention

The preferred embodiments of the present invention are further described in detail below with reference to the accompanying drawings:

Example 1

(1) Disperse 0.5g of 1um aluminum powder in 0.2mol/L 50ml aqueous solution of 18-aqueous aluminum silicate, stir, then gradually add urea and continue to stir until the precipitation no longer increases. After the reaction is complete, filter and precipitate. The material was washed with water and dried at 60 ° C to obtain an Al-Al(OH) ₃ material.

(2) The obtained Al-Al(OH) ₃ material was placed in a muffle furnace at 1100 ° C for high-temperature calcination for 1 hour to obtain hollow alumina.

(3) 15 mg of hollow alumina, 80 mg of sulfur simple substance, and 5 mg of graphene were added to carbon disulfide, ultrasonically dispersed for 0.5 hour to form a suspension, and then the solvent was evaporated to dryness at 40 ° C to obtain a composite material.

Example 2

(1) Disperse 0.5g of 100um aluminum powder in 0.4mol/L of 50ml aqueous solution of 18-aqueous aluminum silicate, stir, then gradually add urea to continue stirring until the precipitation no longer increases. After the reaction is complete, filter and precipitate. The material was washed with water and dried at 60 ° C to obtain an Al-Al(OH) ₃ material.

(2) The obtained Al-Al(OH) ₃ material was placed in a muffle furnace at 900 ° C for high-temperature calcination for 3 hours to obtain hollow alumina.

(3) 30 mg of hollow alumina, 60 mg of sulfur simple substance, and 10 mg of graphene were added to carbon disulfide, ultrasonically dispersed for 5 hours to form a suspension, and then the solvent was evaporated to dryness at 60 ° C to obtain a composite material.

Example 3

(1) Disperse 0.5g of 50um aluminum powder in 0.25mol/L of 50ml aqueous solution of 18-height hydrated aluminum silicate, stir, then gradually add urea and continue stirring until the precipitation no longer increases. After the reaction is complete, filter and precipitate. The material was washed with water and dried at 60 ° C to obtain an Al-Al(OH) ₃ material.

(2) The obtained Al-Al(OH) ₃ material was placed in a muffle furnace at 1000 ° C for high-temperature calcination for 2 hours to obtain hollow alumina.

(3) 23 mg of hollow alumina, 70 mg of sulfur simple substance, and 7 mg of graphene were added to carbon disulfide, ultrasonically dispersed for 1 hour to form a suspension, and then the solvent was evaporated to dryness at 50 ° C to obtain a composite material.

Example 4

(1) Disperse 0.5 g of 10 μm aluminum powder in 0.3 mol/L of 50 mol aqueous solution of 18-hydrated aluminum silicate, stir, then gradually add urea and continue stirring until the precipitation no longer increases. After the reaction is complete, the precipitate is filtered. The material was washed with water and dried at 60 ° C to obtain an Al-Al(OH) ₃ material.

(2) The obtained Al-Al(OH) ₃ material was placed in a muffle furnace at 9,500 ° C for high-temperature calcination for 2.5 hours to obtain hollow alumina.

(3) 20 mg of hollow alumina, 75 mg of sulfur simple substance, and 5 mg of graphene were added to carbon disulfide, ultrasonically dispersed for 2 hours to form a suspension, and then the solvent was evaporated to dryness at 45 ° C to obtain a composite material.

Example 5

(1) Disperse 0.5 g of 20 μm aluminum powder in 0.35 mol/L of 50 mol aqueous solution of 18-hydrated aluminum silicate, stir, then gradually add urea and continue stirring until the precipitation no longer increases. After the reaction is complete, the precipitate is filtered. The material was washed with water and dried at 60 ° C to obtain an Al-Al(OH) ₃ material.

(2) The obtained Al-Al(OH) ₃ material was placed in a muffle furnace at 1050 ° C for high-temperature calcination for 1.5 hours to obtain hollow alumina.

(3) 27 mg of hollow alumina, 65 mg of sulfur, and 8 mg of graphene were added to carbon disulfide, ultrasonically dispersed for 3 hours to form a suspension, and then the solvent was evaporated to dryness at 55 ° C to obtain a composite material.

Electrode preparation and performance test; electrode material, acetylene black and PVDF were mixed in NMP at a mass ratio of 80:10:10, coated on aluminum foil as electrode film, lithium metal plate as counter electrode, CELGARD 2400 as separator, 1 mol /L LiTFSI/DOL-DME (volume ratio 1:1) is an electrolyte, 1mol/L LiNO3 is an additive, assembled into a button-type battery in a filled glove box, and a constant current charge and discharge test is performed using a Land battery test system. . The charge and discharge voltage range is 1-3V, the current density is 1C, and the performance is shown in Table 1.

Table 1

[Table 1]

1 is an SEM image of a positive electrode material prepared by the present invention. It can be seen from the figure that the aluminum oxide coated lithium sulfide particles are uniformly distributed on the surface of the graphene, which is beneficial to improving the electrochemical performance of the material.

The above is a further detailed description of the present invention in connection with the specific preferred embodiments, and the specific embodiments of the present invention are not limited to the description. It will be apparent to those skilled in the art that the present invention may be made without departing from the spirit and scope of the invention. .

Claims

A method for preparing a cathode material of an alumina hollow sphere lithium-sulfur battery, characterized in that the method comprises the following steps:

Step (1) Disperse the aluminum powder in an aqueous solution of aluminum octadecahydrate, stir, and then gradually add urea to continue stirring until the precipitation does not increase. After the reaction is completed, the precipitate is filtered, washed with water, and dried to obtain Al-Al. (OH) 3 material;

Step (2) The obtained Al-Al(OH) 3 material is placed in a muffle furnace for high-temperature calcination, and after completion of the reaction, hollow alumina is obtained;

Step (3) The obtained hollow alumina, sulfur elemental and graphene are added to carbon disulfide, ultrasonically dispersed to form a suspension, and then the solvent is evaporated to obtain a composite material.
The method according to claim 1, wherein the aluminum powder in the step (1) has a particle diameter of from 1 to 100 μm, and the aqueous solution of the eighteen aqueous aluminum silicate solution has a concentration of from 0.2 to 0.4 mol/L.
The method according to claim 1, wherein the temperature of the high temperature calcination in the step (2) is from 900 to 1100 ° C, and the reaction time is from 1 to 3 hours.
The method according to claim 1, wherein the mass ratio of the hollow alumina, sulfur elemental, and graphene in the step (3) is 15-30:60-80:5-10; the ultrasonic dispersion time is 0.5- 5 hours; the temperature of the evaporated solvent was 40-60 °C.