NbN nanodot decorated N-doped graphene as a multifunctional interlayer for high-performance lithium–sulfur batteries

Abstract

The scalable applications of lithium–sulfur (Li–S) batteries are seriously hampered by the shuttling effect of lithium polysulfides (LiPSs) and the safety concern related to lithium dendrites. Herein, we report a lithiophilic and sulfiphilic NbN decorated nitrogen-doped graphene (NbN@NG) interlayer on a commercial polypropylene (PP) separator. Due to the lithiophilic features of NbN nanodots effectively hindering the growth of lithium dendrites, the Li//Li symmetric battery with NbN@NG/PP delivers outstanding stability at 5 mA h cm⁻² over 1100 h. Owing to the polar and conductive NbN nanodots with strong interaction and high catalytic conversion towards LiPSs suppressing the shuttling effect, the Li–S battery with NbN@NG/PP delivers a high discharge capacity of 1284 mA h g⁻¹ at 0.2C and excellent high-rate performance at 2C with a negligible capacity fading of 0.036% per cycle over 500 cycles. The Li–S pouch battery with NbN@NG/PP delivers a capacity of 847 mA h g⁻¹ with a low electrolyte volume/sulfur loading ratio of 6 μL mg⁻¹. Theoretical density functional theory and in situ Raman spectroscopy effectively demonstrate the mechanism for LiPSs conversion. This work provides a new design strategy for multifunctional separators and new insights into the performance-enhancement mechanism towards high-performance shuttle-free and dendrite-free Li–S batteries.