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 (S2–4). 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.