Interconnected carbon nanotube/graphene nanosphere scaffolds as free-standing paper electrode for high-rate and ultra-stable lithium-sulfur batteries

The rational design and fabrication of flexible electrodes with high capacity, high rate capability, and high cycling stability is of urgent need for bendable, wearable, and implantable electronic devices. The integration of conductive nanocarbon as flexible scaffolds is an efficient and effective route toward flexible high-energy-density lithium-sulfur batteries. Herein, a free-standing paper electrode was constructed by rational integration of high conductive super-long carbon nanotubes (CNTs) and nano-sized hollow graphene spheres (GSs) through a room-temperature solution-processable method for lithium-sulfur batteries. The hollow GSs afforded close space to accommodate sulfur species, sustain the volume fluctuation during cycling, and retard the dissolution of polysulfides and parasitic shuttle. The graphene walls of GSs and super-long CNTs synergistically constructed hierarchical short-/long-range electron/ion pathways. Consequently, the as-obtained flexible paper electrode was with a high sulfur utilization of 81% (corresponding to 1346mAhg^-1) at a current density of 0.17Ag^-1 (0.19mAcm^-2), a high-rate capacity retention of 40% when the current density increased to supreme 16.7Ag^-1 (18.4mAcm^-2), and a superior capacity retention of 89.0% over 500 cycles. This proof-of-concept research indicated the well hybridization of graphene and CNTs holds promise in the efficient use as flexible electrodes for future flexible electronics.