Three-Dimensional Honeycomb-Like Carbon as Sulfur Host for Sodium-Sulfur Batteries without the Shuttle Effect

Sodium-sulfur batteries operating at ambient temperature are being extensively studied because of the high theoretical capacity and abundant resources, yet the long-chain polysulfides' shuttle effect causes poor cycling performance of Na-S batteries. We report an annealing/etching method to converse low-cost wheat bran to a 3D honeycomb-like carbon with abundant micropores (WBMC), which is smaller than S₈ molecular size (∼0.7 nm). Thus, the microporous structure could only fill small molecular sulfur (S_2-4). The micropores made sulfur a one-step reaction without the shuttle effect due to the formed short-chain polysulfides being insoluble. The WBMC@S exhibits an excellent initial capacity (1413 mAh g^-1) at 0.2 C, outstanding cycling performance (822 mAh g^-1 after 100 cycles at 0.2 C), and high rate performance (483 mAh g^-1 at 3.0 C). The electrochemical performance proves that the steric confinement of micropores effectively terminates the shuttle effect.