Flexible high-energy-density lithium-sulfur batteries using nanocarbon-embedded fibrous sulfur cathodes and membrane separators

Abstract To obtain soft electronics, it is essential to develop high-performance and mechanically flexible energy storage at the industry level. Herein, we report flexible high-energy-density lithium-sulfur (Li–S) batteries based on all-fibrous sulfur cathodes and separators. To implement free-standing and flexible sulfur cathodes, electrically conductive single-walled carbon nanotubes (CNTs) are impregnated with cellulose nanofibers. This fibrous structure forms a 3D porous electrode with a large surface area to improve redox kinetics and achieve a high sulfur loading content without the use of a metal collector, which can then be applied in high-energy-density batteries. These flexible sulfur cathodes are combined with a commercial glass fiber separator coated with a CNT layer through a cost-effective solution process to suppress the shuttle effects of lithium–polysulfide, thereby exhibiting robust cycling stability. The prepared Li–S batteries exhibit high capacities of 940 mAh g−1 at a charge current density of 1.57 mA cm−2 and at 25 °C, and the Coulombic efficiency exceeds 90% even after 50 charge/discharge cycles. Moreover, Li-S batteries with a high gravimetric energy density of 443 Wh kg−1 per cell is achieved, and these batteries demonstrate excellent reliability in regard to electrochemical performance even under severe mechanical stress conditions for over 100 cycles.