WO2017139991A1

WO2017139991A1 - Preparation method for manganese dioxide hollow sphere lithium-sulphur battery positive electrode material

Info

Publication number: WO2017139991A1
Application number: PCT/CN2016/074187
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

A preparation method for a manganese dioxide hollow sphere lithium-sulphur battery positive electrode material, comprising the following steps: (1) adding manganese chloride, potassium potassium permanganate, and sodium dodecyl benzene sulphonate to distilled water and mixing to dissolve; (2) adding said solution to a hydrothermal kettle to implement a hydrothermal reaction, and after completion of the reaction, cooling naturally, filtering, washing with water, washing with ethanol, and drying to obtain a hollow manganese dioxide; and (3) adding the obtained hollow manganese dioxide, elemental sulphur, and graphene to carbon disulphide, implementing ultrasonic dispersion to form a suspension, and then evaporating the solvent to obtain a composite material. The manganese dioxide hollow spheres in the graphene/manganese dioxide hollow sphere/sulphur composite material are covered with a sulphur base material, and can inhibit the dissolution of polysulphides from the discharge product and mitigate volume expansion, improving electrochemical performance.

Description

Preparation method of manganese dioxide hollow sphere lithium sulfur battery cathode material

Technical field

The invention relates to the synthesis of nano materials, in particular to a preparation method of a cathode material for 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/manganese dioxide hollow sphere/sulfur composite material, which has a simple preparation method, a conductive conductive graphene provides a conductive network, and a hollow structure of manganese dioxide coated with a sulfur-based material. It can prevent the dissolution of the polysulfide of the discharge product and alleviate the volume expansion and improve the electrochemical performance of the material.

Problem solution

Technical solution

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

(1) adding manganese chloride, potassium permanganate, sodium dodecylbenzenesulfonate to distilled water and stirring;

(2) The above solution is added to a hydrothermal kettle for hydrothermal reaction. After the reaction is completed, it is naturally cooled, filtered, washed with water, washed with ethanol, and dried to obtain hollow manganese dioxide.

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

The mass ratio of manganese chloride: potassium permanganate: 120,000-grade sodium benzenesulfonate in step (1) is 20:10-15:0.5-2;

The temperature of the hydrothermal reaction in the step (2) is 160-200 ° C, and the reaction time is 3-10 hours;

Step (3) The mass ratio of hollow manganese dioxide, 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/manganese dioxide hollow sphere/sulfur composite prepared by the method can effectively improve the electronic conductivity of the cathode material of the lithium-sulfur battery. And ionic conductivity; (2) graphene/manganese dioxide hollow sphere/sulfur composite material, the manganese dioxide hollow sphere coated with sulfur-based material, can inhibit the dissolution of the discharge product polysulfide and alleviate the 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/manganese dioxide 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) (1) 500 mg of manganese chloride, 250 mg of potassium permanganate, and 12.5 mg of sodium dodecylbenzenesulfonate are added to distilled water to stir and dissolve;

(2) The above solution was added to a hydrothermal kettle, and hydrothermally reacted at 160 ° C for 10 hours. After the reaction was completed, it was naturally cooled, filtered, washed with water, washed with ethanol, and dried to obtain a hollow manganese dioxide.

(3) 15 mg of hollow manganese dioxide, 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) 600 mg of manganese chloride, 450 mg of potassium permanganate, and 60 mg of sodium dodecylbenzenesulfonate are added to distilled water to stir and dissolve;

(2) The above solution is added to a hydrothermal kettle, and hydrothermally reacted at 200 ° C for 3 hours. After the reaction is completed, it is naturally cooled, filtered, washed with water, washed with ethanol, and dried to obtain hollow manganese dioxide.

(3) 30 mg of hollow manganese dioxide, 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) 800 mg of manganese chloride, 480 mg of potassium permanganate, and 40 mg of sodium dodecylbenzenesulfonate are added to distilled water to stir and dissolve;

(2) The above solution was added to a hydrothermal kettle, and hydrothermally reacted at 170 ° C for 8 hours. After the reaction was completed, it was naturally cooled, filtered, washed with water, washed with ethanol, and dried to obtain a hollow manganese dioxide.

(3) 23 mg of hollow manganese dioxide, 70 mg of sulfur, 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) 600 g of manganese chloride, 390 mg of potassium permanganate, and 45 mg of sodium dodecylbenzenesulfonate are added to distilled water to stir and dissolve;

(2) The above solution is added to a hydrothermal kettle, and hydrothermally reacted at 180 ° C for 6 hours. After the reaction is completed, it is naturally cooled, filtered, washed with water, washed with ethanol, and dried to obtain hollow manganese dioxide.

(3) 20 mg of hollow manganese dioxide, 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) 400 g of manganese chloride, 280 g of potassium permanganate, and 38 mg of sodium dodecylbenzenesulfonate are added to distilled water to stir and dissolve;

(2) The above solution was added to a hydrothermal kettle, and hydrothermally reacted at 190 ° C for 4 hours. After the reaction was completed, it was naturally cooled, filtered, washed with water, washed with ethanol, and dried to obtain a hollow manganese dioxide.

(3) 27 mg of hollow manganese dioxide, 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 LiN03 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, and it can be seen from the figure that the manganese dioxide coated vulcanization The uniform distribution of lithium particles on the surface of graphene is beneficial to improve 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 a manganese dioxide hollow sphere lithium-sulfur battery, characterized in that the method comprises the following steps:

Step (1) adding manganese chloride, potassium permanganate, sodium dodecylbenzenesulfonate to distilled water and stirring;

Step (2) The above solution is added to a hydrothermal kettle for hydrothermal reaction. After the reaction is completed, it is naturally cooled, filtered, washed with water, washed with ethanol, and dried to obtain hollow manganese dioxide.

Step (3) The obtained hollow manganese dioxide, sulfur elemental substance, 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 mass ratio of manganese chloride, potassium permanganate and sodium 120,000-sulfonate in the step (1) is 20:10-15:0.5-2 .
The method according to claim 1, wherein the temperature of the hydrothermal reaction in the step (2) is from 160 to 200 ° C, and the reaction time is from 3 to 10 hours.
The method according to claim 1, wherein the step (3) hollow manganese dioxide, sulfur elemental, graphene mass ratio is 15-30:60-80:5-10; ultrasonic dispersion time is 0.5 -5 hours; the temperature of the evaporated solvent is 40-60 °C. .