Preparation method of graphene-grafted polypyrrole nanotube/sulfur composite material for positive electrode of lithium-sulfur battery

Abstract

The invention relates to a preparation method of a graphene-grafted polypyrrole nanotube / sulfur composite material for a positive electrode of a lithium-sulfur battery. The method includes the following steps of: step 1, preparing a graphene oxide-grafted polypyrrole (GOppy) nanotube; step 2, preparing a graphene-grafted polypyrrole (Gppy) nanotube; and step 3, preparing a graphene-grafted polypyrrole (Gppy) nanotube / sulfur composite material, wherein the step 3 specifically includes the following process of: placing the Gppy nanotube prepared in the step 2 and nano-sulfur powder in a ball mill, performing ball milling treatment for 2-4h, and then placing a mixture obtained by ball milling in a reaction kettle that takes polytetrafluoroethylene as a substrate under the protection of an argon atmosphere, and performing reaction for 1-20h at 100-200 DEG C to prepare a graphene-grafted polypyrrole (Gppy) nanotube / sulfur composite lithium-sulfur battery positive electrode material. The lithium-sulfur battery positive electrode material prepared by the invention can effectively inhibit the shuttle effect, and can further generally improve the electrochemical performance and cycle stability of the lithium-sulfur battery.

Description

Technical field [0001] The present invention relates to the technical field of lithium-sulfur battery cathode materials, in particular to a method for preparing graphene grafted polypyrrole (Gppy) nanotube / sulfur composite material for lithium-sulfur battery anodes. Background technique [0002] As a device for energy storage and conversion, the battery has played an irreplaceable role in people's life and social production, especially in the field of mobile electronic equipment, and has received extensive attention. Lithium-ion batteries have the characteristics of high energy density, long service life and environmental protection, and have been successfully commercialized. Currently, the commercial cathode materials for lithium-ion batteries are mainly: LiCoO2, LiMnO2, layered Li(Ni1 / 3Co1 / 3Mn1 / 3)O2 ternary materials, spinel-type LiMn2O4 and olivine-type LiFePO4. However, the above materials have their own disadvantages when used as lithium ion battery cathode materials. For ...

AI Technical Summary

Problems solved by technology

The main problems are: (1) The conductivity of sulfur and the discharge product lithium sulfide is poor, which makes it difficult for the battery to charge and discharge under high rate conditions; When the volume expands, it affects the performance of the battery; (3) the discharge intermediate product lithium polysulfide is easily soluble in the electrolyte, resulting in irreversible attenuation of the battery capacity; (4) the discharge intermediate product lithium polysulfide dissolved in the electrolyte is In the process, under the action of concentration difference and electric field, it diffuses back and forth between the positive and negative electrodes and undergoes a redox reaction, and part of lithium polysulfide is reduced to insoluble solid lithium sulfide on the surface of the negative electrode, resulting in a decrease in the Coulombic efficiency of the battery; (5) The metal lithium negative electrode forms lithium dendrites during the charge and discharge process, piercing the SEI film, and the SEI film is repeatedly formed-ruptured, constantly consuming the electrolyte, and may puncture the separator and cause a short circuit in the battery in severe cases

Chinese patent CN106159209A discloses a method for preparing a graphene-containing sulfur-based composite positive electrode material that can be used for the positive electrode of a lithium-sulfur battery. The method uses nickel foam as a template and graphite oxide as a precursor to prepare a foamed graphene / sulfur composite material. Elemental substances can be effectively attached in the pores of foamed graphene, which increases the capacity of the battery. However, the graphene involved in this process is a two-dimensional non-polar material, and its adsorption capacity for polysulfide intermediates is not strong, so it is difficult to effectively Inhibition of the shuttle effect

Chinese patent CN107275580A discloses a method for preparing a polyaniline / sulfur composite material that can be used for the positive electrode of a lithium-sulfur battery. The method uses aminothiophenol as a raw material and ammonium persulfate as an initiator to prepare a conductive polymer polyaniline, and then passes The sulfur-based positive electrode material was prepared by melting sulfur doping method. The carbon-nitrogen bond on polyaniline is polar, and the nitrogen element can provide additional lone pair electrons, which can adsorb lithium polysulfide, an intermediate product of lithium-sulfur battery discharge, thereby improving the battery cycle. performance, but this method has the following disadvantages: (1) aminothiophenol will be irreversibly stacked during the polymerization into polyaniline, resulting in low porosity and low specific surface area of ​​the polyaniline material, which is not conducive to the attachment of sulfur on it; (2) In this method, the temperature is kept at 175°C for 8 hours during melting and sulfur mixing. This temperature is higher than the melting point of sulfur, which will cause the loss of sulfur, resulting in a decrease in energy density.

Chinese patent CN106848319A discloses a method for preparing a rutile titanium dioxide-titanium nitride / sulfur composite material that can be used for the positive electrode of lithium-sulfur batteries. The method uses titanium tetrachloride and urea as raw materials to prepare heterojunction nanomaterials, and then passes Sulfur-based cathode materials were prepared by molten sulfur doping method. In this material, titanium dioxide and carbon nitride are doped symbiotic structures, which can adsorb polysulfides, thereby improving the cycle performance of lithium-sulfur batteries. However, whether it is carbon dioxide or titanium nitride The electrical conductivity is very poor, it is difficult to meet the requirements of lithium-sulfur batteries for high rate performance

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