Long-life, high-efficiency lithium/sulfur batteries from sulfurized carbon nanotube cathodes

Abstract

The long-term cycling properties of Li–S cells comprised of sulfurized carbon nanotubes (SCNTs) were thoroughly investigated. A high concentration (68 wt%) of sulfur was successfully immobilized on the surfaces of functionalized CNTs using a unique fabrication method that combined solvent exchange and surface and low-temperature treatments. The developed Li–S cells presented a long cycle life exceeding 1300 cycles and an extremely low capacity decay rate (0.025% per cycle) at 1/3 C rate. Moreover, these Li–S cells had an excellent high-rate response up to 2 C with high Coulombic efficiency (above 95.5%) and high sulfur utilizations (1180 mA h g⁻¹ of sulfur over 300 cycles at 0.25 C, 799 mA h g⁻¹ over 600 cycles at 0.75 C, 810 mA h g⁻¹ over 500 cycles at 1 C, and 400 mA h g⁻¹ over 500 cycles at 2 C). These results provide important progress towards understanding the role of SCNTs in developing Li–S batteries with potentially high efficiency and long-term service life.