Porous carbon sphere packaged vanadium oxide heterogeneous core-shell sphere structure material and preparation method thereof, lithium-sulfur battery diaphragm and lithium-sulfur battery

Abstract

The invention belongs to the field of electrochemical materials, and provides a porous carbon sphere packaged vanadium oxide heterogeneous core-shell sphere structure material and a preparation method thereof, a lithium-sulfur battery diaphragm and a lithium-sulfur battery. The preparation method of the porous carbon sphere encapsulated vanadium oxide heterogeneous core-shell sphere structure material comprises the following steps: stirring water, ethanol, ammonia water, tetraethyl orthosilicate, resorcinol and formaldehyde, carrying out a stirring reaction to obtain a carbon-coated silicon dioxide core-shell structure, carbonizing the carbon-coated silicon dioxide core-shell structure, adding the carbon-coated silicon dioxide core-shell structure into a sodium hydroxide solution to obtain a hollow porous carbon sphere, mixing ammonium metavanadate, ethanol and nitric acid to obtain a vanadium oxide solution, adding the hollow porous carbon spheres into the vanadium oxide solution, and carrying out ultrasonic treatment and hydrothermal reaction to obtain a product. According to the invention, the amount of a vanadium oxide precursor entering porous carbon spheres is controlled by adjusting ultrasonic time so as to achieve manual control of a nano structure, and the product takes the non-polar carbon spheres as a surface layer so as to achieve an adsorption effect on polysulfide and show high conversion efficiency when sulfur exists in the inner layer.

Description

technical field [0001] The invention belongs to the field of electrochemical materials, and in particular relates to a porous carbon sphere-encapsulated vanadium oxide heterogeneous core-shell sphere structure material and a preparation method thereof, a lithium-sulfur battery diaphragm and a lithium-sulfur battery. Background technique [0002] Lithium-sulfur batteries have high theoretical energy density (2600Wh kg-1) and specific capacity (1675 mAh g-1). In addition, sulfur has low toxicity and environmental friendliness, and is cheap, so lithium-sulfur batteries are considered to be the most Potential next-generation energy storage system. However, lithium-sulfur batteries also have the following problems: First, due to uneven lithium deposition, lithium dendrites will be formed during the cycle, resulting in damage, deactivation or even "dead lithium" of the lithium anode, which greatly increases the concentration of the electrolyte. Consumption, reducing the reversibi...

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Problems solved by technology

However, lithium-sulfur batteries also have the following problems: First, due to uneven lithium deposition, lithium dendrites will be formed during the cycle, resulting in damage, deactivation or even "dead lithium" of the lithium anode, which greatly increases the concentration of the electrolyte. Consumption, reducing the electrolyte and the reversibility of the lithium anode

In addition, the sharp Li dendrites can pierce the separator leading to short circuits and thermal runaway.

Second, the volume expansion during charging and discharging is large (~79%), resulting in easy damage to the structure

The third is that the sulfur cathode will generate soluble lithium polysulfides (LiPSs) during charge and discharge, and its conductivity is low.

[0004] At present, one of the functional modification methods of the separator is to use porous materials to modify the separator, such as porous carbon, but most of these conductive materials are non-polar, and the adsorption of polysulfides is mainly physical adsorption, and the Coulombic efficiency is low.

The second is to use elements doped (such as N) carbon, sulfide and other materials to modify the separator, so that the separator has a strong chemical adsorption capacity, which can effectively capture LiPSs in the electrolyte, but the amount of LiPSs adsorbed and captured is different from that of the modified materials. Therefore, the more the amount of LiPSs adsorbed and captured, the thicker the thickness of the separator modification layer will seriously affect the diffusion of ions, thus greatly reducing the rate performance.

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