Surface-Modified Sulfur Nanorods Immobilized on Radially Assembled Open-Porous Graphene Microspheres for Lithium-Sulfur Batteries.

The assembly of two-dimensional conductive nanomaterials into hierarchical complex architectures precisely controlling internal open porosity and orientation, external morphology, composition, and interaction is expected to provide promising hosts for high-capacity sulfur cathodes. Herein, we demonstrate rod-like nanosulfur (nS) deposited onto radially oriented open-porous microspherical reduced graphene oxide (rGO) architectures for improved rate and cyclic capabilities of lithium-sulfur (Li-S) batteries. The combined chemistry of a spray-frozen assembly and ozonation drives the formation of a radially oriented open-porous structure and an overall microspherical morphology as well as uniform distribution and high loading of rod-like nS. Moreover, an optimum composition and strong bonding of the rGO/nS hybrid enables the optimization of redox kinetics for high sulfur utilization and high-rate capacities. The resulting rGO/nS hybrid provides a specific capacity and first-cycle Coulombic efficiency of 1269.1 mAh g-1 and 98.5%, respectively, which are much greater than those of ice-templated and physically mixed rGO/nS hybrids and radially oriented open-porous rGO/bulk sulfur with the same hybrid composition. A 4C capacity of 510.3 mAhg-1 and capacity decay of 0.08% per cycle over 500 cycles (70.9% of the initial capacity over 300 cycles) also support the synergistic effect of the rod-like nS strongly interacting with the radially oriented open-porous rGO microspheres.