Electrochemical Conversion of Confined 1D Sulfur Chains in Li–S Battery

Abstract Lithium–sulfur (Li–S) batteries are prospective as one of the most promising candidates for next‐generation energy storage systems owing to high energy density and cost‐effectiveness. Compared with normal bulk sulfur, the electrochemistry behaviors of sulfur chains inside single‐wall carbon nanotubes (SWCNTs) have rarely been investigated. Herein, one type of 1D sulfur chain encapsulated in SWCNTs (S@SWCNTs) is designed as the cathode for Li–S batteries. Experimental studies and density functional theory (DFT) calculations reveal the suppressed shuttle effect and the accelerated sulfur reduction kinetics in S@SWCNTs cathodes, benefiting from the spatial confinement effect of SWCNTs. The S@SWCNTs electrode possesses an excellent rate performance and highly reversible discharge capacity of 1123 mAh g⁻¹ at 1 C with 0.07% capacity fade rate per cycle over 500 cycles. Moreover, the S@SWCNTs as the self‐supporting cathodes can still exhibit capacity retention of 94% after 100 cycles with a high sulfur loading of 5.84 mg cm⁻² and low E/S (electrolyte/sulfur) ratio of 4.3 µL mg⁻¹, promising for high energy‐density full batteries. This work helps the understanding of sulfur chain redox reaction and electrochemistry behaviors inside SWCNTs and provides a path‐breaking vision to develop the cathodes of Li–S batteries.