Enriched vacancies of ruthenium doped niobium oxide on hollow graphene sphere as sulfur reduction reaction promoter in lithium sulfur batteries

Inhibiting the shuttle effect of soluble polysulfides (LiPSs) is critical to lithium–sulfur (Li–S) batteries. Nevertheless, the conventional separator fails to block immigration of LiPSs between electrodes. Herein, the enriched oxygen vacancies were stabilized with ruthenium doping on niobium oxide/three-dimensional reduced graphene oxide nanosphere (Nb2O5−x/Ru-3DG) to prepare a functional separator layer for LiPSs diffusion prevention. The inhibition mechanism is unraveled by density functional theoretical calculations and experimental results. Li–S batteries with Nb2O5−x/Ru-3DG-based separator displayed an excellent capacity of 700.3 mAh g−1 with a long-term stability of 1000 cycles and a high rate-performance of 533.2 mAh g−1 at 8 C. An industrial-level pouch cell delivered an outstanding specific capacity of 925.8 mAh g−1 with an exceptional flexibility. This study could open a new strategy to design materials with controlled defects and doping for LiPSs immobilization, enhanced catalytic activities for redox reaction, and other catalysts for energy conversion and storage devices.