Multifunctional G@UC3N4 modified separator for high-performance Li-S batteries.

Lithium-sulfur batteries (LSBs) are known for their outstanding theoretical energy density and low cost. However, low sulfur utilization and shuttle effect of the lithium polysulfides (LiPSs) dissolved in the electrolyte seriously limit its commercialization. Herein, graphene@carbon nitride (G@UC 3 N 4) composite modified separator is designed as a multifunctional barrier to enhance the performance of LSBs. UC 3 N 4 with high specific surface area and high pyridinic nitrogen (N) content is prepared by simple secondary heat treatment method, achieving a double physical-chemical limitation for the shuttle of LiPSs. Meanwhile, graphene as a carrier for UC 3 N 4 not only enhances the conductivity of the entire electrode but also accelerates the diffusion of Li+ and the penetration process of the electrolyte. LSBs assembled with G@UC 3 N 4 polypropylene separator exhibit high initial specific capacity (1216.46 mAh g−1 at 1 C) and stable long cycling capability (average decay rate of only 0.047% after 1000 cycles at 2 C, with a coulombic efficiency consistently above 99%). • A porous G@UC 3 N 4 nanocomposite is used as multifunctional interlayer on PP separator. • G@UC 3 N 4 modified separator accelerate the diffusion of Li+ and the penetration process of the electrolyte. • G@UC 3 N 4 modified separator can selectively block polysulfides and promote their conversion. • A Li–S cell assembled with G@UC 3 N 4 modified separator shows obviously improved performance. [ABSTRACT FROM AUTHOR]