A Promising Approach to Ultra‐Flexible 1 Ah Lithium–Sulfur Batteries Using Oxygen‐Functionalized Single‐Walled Carbon Nanotubes

Abstract Lithium–sulfur (Li‐S) batteries represent a promising solution for achieving high energy densities exceeding 500 Wh kg −1 , leveraging cathode materials with theoretical energy densities up to 2600 Wh kg −1 . These batteries are also cost‐effective, abundant, and environment‐friendly. In this study, an innovative approach is proposed utilizing highly oxidized single‐walled carbon nanotubes (Ox‐SWCNTs) as a conductive fibrous scaffold and functional interlayer in sulfur cathodes and separators, respectively, to demonstrate large‐area and ultra‐flexible Li‐S batteries with enhanced energy density. The free‐standing sulfur cathodes in the Li‐S cells exhibit high energy density maintaining 806 mAh g −1 even after 100 charge‐discharge cycles. Additionally, oxygen‐containing functional groups on the SWCNTs significantly improve electrochemical performance by promoting the adsorption of lithium polysulfides. Employing Ox‐SWCNTs in both cathodes and interlayers, the study achieves high‐capacity Li‐S pouch cells that consistently deliver a capacity of 1.06 Ah and a high energy density of 909 mAh g −1 over 50 charge‐discharge cycles. This strategy not only significantly enhances the electrochemical performance of Li‐S batteries but also maintains excellent mechanical flexibility under severe deformation, positioning this Ox‐SWCNT‐based architecture as a viable, light‐weight, and ultra‐flexible energy storage solution suitable for commercializing rechargeable Li‐S batteries.