Sulfur-nitrogen doped carbon nanofiber-MXene composite material for lithium-sulfur battery and preparation method thereof

Abstract

The invention relates to a sulfur-nitrogen doped carbon nanofiber-MXene composite material for a lithium-sulfur battery and a preparation method thereof. Mxene doped polyacrylonitrile nanofiber is prepared by an electrospinning technology, a nitrogen-doped carbon nanofiber-MXene composite material is obtained by high-temperature carbonization, and the sulfur-nitrogen doped carbon nanofiber-MXene composite material is prepared through sulfur doping by a ball-milling and hot melting method. When the composite material obtained by preparation is used as the positive electrode material applied toa lithium-sulfur battery, lithium polysulfide can be effectively absorbed, and the beneficial effects of suppressing a shuttle effect and reducing volume expansion during the charge-discharge processare achieved.

Description

Technical field [0001] The technical scheme of the present invention relates to a method for preparing a lithium-sulfur battery positive electrode material with a high specific capacity, in particular to a method for preparing MXene-doped polyacrylonitrile nanofibers by an electrostatic spinning method, and then performing high-temperature calcination to obtain nitrogen doping The method of carbon nanofiber-MXene composite lithium-sulfur battery cathode material belongs to the field of material chemistry. Background technique [0002] With the successful commercial use of graphite anodes, lithium-ion batteries have been widely used in portable electronic devices such as smart phones, laptops, and so on. After more than 20 years of development, the existing lithium-ion batteries based on lithium-intercalation compound cathodes are close to their theoretical capacity, but they still cannot meet the requirements of the fast-developing electronics industry and emerging electric vehic...

AI Technical Summary

Problems solved by technology

Studies have shown that the dissolution and diffusion of a large amount of polylithium sulfide in the electrolyte will lead to the loss of positive active materials and reduce the cycle life of the battery; in addition, the discharge product lithium sulfide Li 2 S 2 and Li 2 S will precipitate from the organic electrolyte and cover the surface of the sulfur cathode, forming an insulating lithium sulfide film, which hinders the discharge reaction between the electrolyte and the electrode active material.

(3) The chemical properties of metal lithium are very active, and it is easy to react with the electrolyte solution, and an SEI film is formed on the surface of the electrode material, resulting in an increase in the polarization resistance of the electrode; the dissolved high-polymer polysulfide will diffuse to the lithium surface and form a self-reaction with lithium. The discharge corrosion reaction leads to irreversible capacity loss of the active material; at the same time, the reduction product of some oligomerization states diffuses back to the positive electrode under the action of the concentration gradient for re-oxidation, thereby producing the shuttle effect and reducing the electric Coulombic efficiency.

In addition, part of lithium will lose its activity during charging and discharging, and become irreversible "dead lithium"; and due to the inhomogeneity of the electrode surface, lithium dendrites may be formed, causing safety problems.

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