Nb2 O5 /RGO Nanocomposite Modified Separators with Robust Polysulfide Traps and Catalytic Centers for Boosting Performance of Lithium-Sulfur Batteries.

Lithium-sulfur batteries (LSBs) have shown great potential for application in high-density energy storage systems. However, the performance of LSBs is hindered by the shuttle effect and sluggish reaction kinetics of lithium polysulfides (LiPSs). Herein, heterostructual Nb2 O5 nanocrystals/reduced graphene oxide (Nb2 O5 /RGO) composites are introduced into LSBs through separator modification for boosting the electrochemical performance. The Nb2 O5 /RGO heterostructures are designed as chemical trappers and conversion accelerators of LiPSs. Originating from the strong chemical interactions between Nb2 O5 and LiPSs as well as the superior catalytic nature of Nb2 O5 , the Nb2 O5 /RGO nanocomposite possesses high trapping efficiency and efficient electrocatalytic activity to long-chain LiPSs. The effective regulation of LiPSs conversion enables the LSBs enhanced redox kinetics and suppressed shuttle effect. Moreover, the Nb2 O5 /RGO nanocomposite has abundant sulfophilic sites and defective interfaces, which are beneficial for the nucleation and growth of Li2 S, as evidenced by analysis of the cycled separators. As a result, LSBs with the Nb2 O5 /RGO-modified separators exhibit excellent rate capability (816 mAh g-1 at 3 A g-1 ) and cyclic performance (628 mAh g-1 after 500 cycles). Remarkably, high specific capacity and stable cycling performance are demonstrated even at an elevated temperature of 50 °C or with higher sulfur loadings.