Ultrathin MnO2 Nanosheets Coated Multifunctional Separator for Lithium-Sulfur Batteries Showing High Stability.

Abstract

The shuttling of dissolved polysulfides for the cathode and the growth of lithium dendrites for the anode have caused severe capacity loss and safety risks in Li-S batteries, thus hindering their 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 in the 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 ultrastable cycling performance with a capacity decay of only 0.07% per cycle over 500 cycles at 2 C. Even under high sulfur loading of 4.6 mg cm^-2 and low E/S ratio of 8 μL mg^-1, the battery with the MnO₂ nanosheets modified separator demonstrates a high capacity of 748.7 mAh g^-1 at 0.5C. This work provides valuable insights for the rational design of multifunctional separators in high energy density Li-S batteries.