Ultrathin MnO2 nanosheets coated multifunctional separator for lithium-sulfur batteries showing high stability
Abstract
The shuttling of dissolved polysulfides for cathode and the growth of lithium dendrites for anode have caused severe capacity loss and safety risks of Li-S battery, thus hindering its practical application. To address these issues, we construct a multifunctional separator utilizing ultrathin MnO2 nanosheets with abundant exposed active sites, which enables efficient polysulfide chemical adsorption and catalytic conversion. Additionally, the lithiophilic nature of MnO2 homogenizes the interfacial Li+ flux, resulting in high Li+ conductivity and fast diffusion of modified separator to inhibit lithium dendrites. Moreover, the modified PP separator enhances the battery's energy density due to its ultrathin MnO2 coating with minimal weight (~1 μm on each side, 0.04 mg cm-2) compared to separators modified with high-mass coatings. As a result, the Li-S battery utilizing the MnO2 nanosheets modified separator delivers ultra-stable cycling performance with a capacity decay of only 0.07% per cycle over 500 cycles at 2C. Even under high sulfur loading of 4.6 mg cm-2 and low E/S ratio of 8 μL mg-1, the battery with MnO2 nanosheets modified separator demonstrates a high capacity of 748.7 mAh g-1 at 0.5C. This work provides valuable insights for rational design of multifunctional separators in high energy density Li-S batteries.
