TiO2 and Co Nanoparticle-Decorated Carbon Polyhedra as Efficient Sulfur Host for High-Performance Lithium-Sulfur Batteries

Metal organic frameworks (MOFs)-derived porous carbon is proposed as a promising candidate to develop novel, tailorable structures as polysulfides immobilizers for lithium-sulfur batteries because of their high-efficiency electron conductive networks, open ion channels, and abundant central ions that can store a large amount of sulfur and trap the easily soluble polysulfides. However, most central ions in MOFs-derived carbon framework are encapsulated in the carbon matrix so that their exposures as active sites to adsorb polysulfides are limited. To resolve this issue, highly dispersed TiO2 nanoparticles are anchored into the cobalt-containing carbon polyhedras that are converted from ZIF-67. Such a type of TiO2 and Co nanoparticles-decorated carbon polyhedras (C-Co/TiO2) provide more exposed active sites and much stronger chemical trapping for polysulfides, hence improving the sulfur utilization and enhancing reaction kinetics of sulfur-containing cathode simultaneously. The sulfur-containing carbon polyhedras decorated with TiO2 nanoparticles (S@C-Co/TiO2) show a significantly improved cycling stability and rate capability, and deliver a discharge capacity of 32.9% higher than that of TiO2-free S@C-Co cathode at 837.5 mA g(-1) after 200 cycles.