Silicon/silicon dioxide nanocomposite material wrapped in porous carbon spheres and its preparation method and application

Abstract

The invention provides a porous carbon spheres-coated silicon / silicon dioxide nano-composite material and a preparation method and an application thereof. The porous carbon spheres-coated silicon / silicon dioxide nano-composite material comprises a silicon / silicon dioxide nano-composite material and porous carbon spheres, wherein the porous carbon spheres coat the silicon / silicon dioxide nano-composite material and comprise micropores and mesopores. The porous carbon spheres-coated silicon / silicon dioxide nano-composite material can form physical and chemical adsorption on polysulfide when used as an anode material for a lithium-sulfur battery, is high in sulfur loading capacity and demonstrates excellent electric capacity and cycling stability; and active materials are not easy to lose.

Description

technical field [0001] The invention relates to a nanocomposite material, in particular to a silicon / silicon dioxide nanocomposite material wrapped by porous carbon spheres and its preparation method and application. Background technique [0002] A lithium-sulfur battery is a lithium battery that uses sulfur as the cathode and metal lithium as the anode. When the lithium-sulfur battery is discharged, the anode reaction is that lithium loses electrons to become lithium ions, and the cathode reaction is that sulfur reacts with lithium ions and electrons to form sulfide. The potential difference between the cathode and anode reactions is the discharge voltage provided by the lithium-sulfur battery. The theoretical energy density of lithium-sulfur batteries is more than five times that of lithium-ion batteries, with a value of about 2600Wh / kg. In addition, the theoretical capacity of lithium-sulfur batteries can be as high as 1672mAh / g, and has the advantages of high environmen...

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Problems solved by technology

[0003] Although lithium-sulfur batteries have the above advantages, there are still the following problems: 1. The electronic conductivity and ionic conductivity of elemental sulfur are poor, and the conductivity of sulfur materials at room temperature is extremely low (10 -30 S / cm), and the final product of the reaction Li 2 S 2 and Li 2 S is also an electronic insulator, which is not conducive to the high rate performance of the battery; 2. The intermediate discharge products (polysulfide intermediates or polysulfide anions) of lithium-sulfur batteries will dissolve into the organic electrolyte, which will not only reduce the ion conductivity, but also 3. Sulfur and lithium sulfide have a volume change of up to 80% during charge and discharge, which will lead to changes in the morphology and structure of the cathode, and lead to the detachment of sulfur from the conductive framework, resulting in Capacity attenuation; 4. Lithium-sulfur batteries are still in the laboratory research stage, and the sulfur load per unit area is low

[0005] Although the above methods can improve the cycle performance of lithium-sulfur batteries to a certain extent, the improvement range is limited. The main reason may be that the above-mentioned materials lack the adsorption potential to strongly adsorb polysulfide intermediates, so there is still a loss of active materials.

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