MnO2 nanoflowers grown on a polypropylene separator for use as both a barrier and an accelerator of polysulfides for high-performance Li-S batteries.

The separator modification has been considered to be the most effective approach to obtain high-stability lithium-sulfur batteries (LSBs). Therefore, a separator with an ultralight modification layer plays an indispensable role to obtain LSBs with high specific capacity and high energy density. Herein, we report a novel modified separator with an ultrathin and lightweight MnO2 functional layer (500 nm, 0.1 mg cm-2), which was grown in situ on a Celgard-2400 separator (MnO2@PP) via a facile hydrothermal reaction. The MnO2@PP separator effectively suppressed the shuttle of lithium polysulfides (LiPSs) and improved the redox process. In addition, the strong chemical affinity of MnO2 for LiPSs was also verified by first-principles calculations. Benefiting from these advantages, the cell with the MnO2@PP separator delivered a high rate performance of 759 mA h g-1 at 2.5 C and an initial capacity of 825 mA h g-1 with a retention of 684 mA h g-1 after 400 cycles at 1.25 C. Even with a high sulfur loading of 6 mg cm-2, the obtained cell exhibited a reversible capacity of 747 mA h g-1 after 150 cycles.