Inhibited shuttle effect by functional separator for room-temperature sodium-sulfur batteries

According to a statistic, approximately 6 trillion cigarettes are smoked each year all over the world, which produces approximately 1.2 million tons of discarded cigarette butts. The discarded cigarette filters are non-biodegradable, thus they produce a mass of waste disposal and cause environmental pollution issue. For the purpose of transforming waste into wealth and reducing environmental pollution, nitrogen and sulfur co-doped carbon nanofiber/carbon black (N,S-CNF/CB) composite derived from the discarded cigarette filters is employed to modify glass fiber (GF) separator for the first time in this study. N,S-CNF improves binding ability towards sodium polysulfides (SPSs) by chemisorption. Non-polar CB limits the dissolution of SPSs in the liquid electrolyte by physisorption. The experiment and density functional theory calculation results indicate that a RT-Na/S battery with a N,S-CNF/CB+GF separator exhibits good cycling stability and rate performance. After 100 cycles at a low current rate of 0.1 C, a RT-Na/S battery with a sulfur mass fraction of 71% delivers a discharge capacity of 703 mAh g− 1. In addition, at a high current rate of 0.5 C, a discharge capacity of 527 mAh g− 1 is still maintained after 900 cycles with a very low capacity fading rate of 0.035% per cycle.