Simultaneous Suppression of Shuttle Effect and Lithium Dendrite Growth by Lightweight Bifunctional Separator for Li–S Batteries

The practical use of lithium–sulfur battery (LSB) is impeded by the excessive growth of Li dendrite in the anode and the dissolution of soluble intermediates (shuttle effect) in the cathode. In spite of efforts to overcome these issues, separate research in the anode and cathode fields could not tackle the problems of both electrodes simultaneously, limiting the realization of LSB. Herein, a bifunctional separator is fabricated by coating morphology-controlled NbN on a Celgard separator. The large surface area (67 m2 g–1) and strong adsorptive surface of NbN effectively suppress the crossover of soluble intermediates to the anode side, and the captured sulfur species can be reactivated on the electrical conductive NbN surface to enhance the capacity. Most importantly, the improved mechanical strength and electrolyte wettability of separator by NbN functional layer suppress the growth of Li dendrite in anode. Consequently, even with sulfur loading of 4 mg cm–2, the capacity decay per cycle reaches only 0.061% during 300 cycles at 1 C rate.