| Abstract Scope |
Room-temperature sodium-sulfur batteries hold great promise as the next-generation cost-effective energy storage systems. However, their practical implementation is still plagued by the low reversible capacity of a bulk-sized commercial sulfur cathode with low Coulombic efficiency and poor cycling stability. Here, we present a highly stable room-temperature sodium-sulfur battery using a facile-processed, nanocarbon-promoted, bulk-sized commercial sulfur cathode. This processed nanocarbon possesses a high binding affinity to sulfur and polysulfides, largely facilitating the sulfur reaction kinetics and leading to high reversible capacity. DFT calculation demonstrates that the abundant defects in the processed nanocarbon could contribute to the increased sulfur cathode capacity. Meanwhile, by applying a thin coating of the defect-rich nanocarbon on the polymer electrolyte, dead sulfur formation can be avoided, contributing to greatly enhanced capacity retention. The sodium-sulfur battery delivers a reversible capacity of >700 mAh/g with near-100% Coulombic efficiency and ultrahigh capacity retention of 98.2% at 0.2C after 200 cycles. |