A Nano Rod-Like Α-Mno2 Supported on Carbon Nanotubes Modified Separator Inhibiting Polysulfide Shuttle in Li-S Batteries

Abstract

Lithium-sulfur (Li-S) batteries have attracted enormous attentions as new-generation energy storage devices due to their high theoretical energy density, high theoretical specific capacity, low cost and environmental friendliness. However, polysulfide shuttle and the growth of lithium dendrites significantly restrain the practical application of the Li-S batteries. In this work, a modified PP separator with nanoscale rod-like α-MnO2 supported on carbon nanotubes was prepared. The α-MnO2@CNT modified separator can effectively inhibit the shuttle of polysulfide, enhance the electrochemical activity and accelerate the transfer of ions and electrons. The density functional theory (DFT) calculations demonstrate that α-MnO2@CNT can efficiently adsorb and catalyze the conversion of polysulfides. Due to these advantages, the α-MnO2@CNT-based Li-S battery delivers a initial discharge capacity of 1469 mAh g-1 at 0.05C, 1039 mAh g-1 at 0.5C and the capacity can still maintain 648 mAh g-1 over 500 cycles at 0.5C (capacity decay rate of 0.075%). Expressly, the capacity decay rate is only 0.022% after 600 cycles at a high current density of 2C. The excellent performance could be attributed to the α-MnO2@CNT modified separator not only accelerating the transmission of electrons but also effectively inhibiting the shuttle of polysulfides. Moreover, this work provides a better idea for practical applications of lithium-sulfur batteries in the future.

Keywords: lithium-sulfur battery, α-MnO2@CNT, modified separator, low decay rate