The catalytic activity of manganese dioxide supported on graphene promoting the electrochemical performance of lithium-sulfur batteries

Abstract

Lithium-sulfur (Li-S) batteries have become a research hotspot due to their high energy density, environment friendliness and low-cost. But commercial applications are hampered by rapid capacity fading and low sulfur content. Herein, the composite of integrating manganese oxide on graphene was prepared by a facile redox reaction between potassium permanganate (KMnO4) and graphene in acidic aqueous solution to solve the problems of the Li-S batteries. X-ray Diffraction (XRD), Scanning Electron Microscope (SEM) and transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) analysis show that sulfur was uniformity coated on G/MnO2 composite. TG indicated that the G/MnO2/S composites contained 76.56wt% active sulfur. The prepared cathode of G/MnO2/S composites exhibited excellent rate performance and cycle stability. At a high rate of 1C, its maximum discharge capacity reached 908mAhg−1 and its average capacity decreasing rate was only 0.105%/cycle when running over 500cycles. The interaction mechanism of MnO2 with polysulfides was investigated by adsorption tests and XPS analysis. The excellent electrochemical performance might be due to a combination of adsorption or catalytic properties of MnO2, and the conductivity network of graphene.