Preparation and Application of Manganese Dioxide/Graphene Composite in Lithium Sulfur Batteries

Abstract

Graphene/manganese dioxide composites and grapheme /manganese dioxide/sulfur (G/MnO₂/ S) composite cathode were prepared by hydrothermal method and by vapor permeation, respectively. Their structure, morphology and specific surface area were characterized by X-ray diffraction, electron microanalysis and nitrogen adsorption analysis. The composites show morphology of nanosheets, high specific surface area and even distribution of sulfur. The sulfur accounts for 75% in the G/ MnO₂/S composite by thermogravimetric analysis. The electrochemical performance of G/S and G/ MnO₂/S cathode were investigated. The G/ MnO₂/ S composite cathodes show excellent rate performance and cycle stability. At a 0.2C current density, initial discharge specific capacity is 1 061 mA·h·g⁻¹ and maintains 698 mA·h·g⁻¹ after 100 cycles; At a 1C current density, maximum discharge capacity reaches 816 mA·h·g⁻¹ and average capacity decreasing rate is only 0.073%/ cycle after running over 400 cycles. Electrochemical mechanism of the composites cathodes was analyzed. The sulfur adsorption of MnO₂ inhibited the loss of active material sulfur, so, the electrochemical performance of the complex was improved.

Keywords

manganese dioxide / grapheme / electrochemical performance / lithium-sulfur batteries