Designing a Multifunctional Separator for High-Performance Li-S Batteries at Elevated Temperature.

The practical applications of lithium-sulfur (Li-S) batteries are seriously limited by the undesirable polysulfide shuttling and lithium dendrite growth. Herein, a multifunctional membrane is designed and prepared by coating a lithiated Nafion (Li@Nafion) layer and an Al2 O3 layer on the two sides of a routine polymer membrane (polypropylene/polyethylene/polypropylene, PEP). The Li@Nafion layer faced to the sulfur cathode builds a "polysulfide-phobic" surface to restrain the shuttle effect via Coulomb repulsion, while the Al2 O3 layer with a uniform porous structure aids in regulating homogeneous Li+ fluxes to achieve stable Li electrodeposition. As a result, the Li//Li symmetric cell with a Li@Nafion/PEP/Al2 O3 (LNPA) separator realizes stable Li plating/striping even after 1000 h at a high current density (5 mA cm-2 ). Moreover, the Li-S batteries incorporating LNPA separators not only can achieve excellent outstanding cyclic stability at an ultrahigh sulfur loading (7.6 mg cm-2 ), but also exhibit impressive electrochemical performance at an elevated temperature (60 °C). The rational design of the LNPA separator presents new insights to develop high-performance Li-S batteries.