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

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.