Cobalt-doped oxygen-deficient titanium dioxide coated by carbon layer as high-performance sulfur host for Li/S batteries

Abstract

The severe shuttle effect and sluggish conversion kinetics of lithium polysulfides impede the commercialization of lithium/sulfur (Li/S) batteries. To address this issue, a composite consists of Co-doped oxygen-deficient TiO2 coated by carbon layer (Co/TiO2-x@carbon) is proposed as a high-performance sulfur host. It was fabricated by one-step hydrothermal synthesis, follow by chemical vapor deposition method. The oxygen defects on the surface of Co/TiO2-x@carbon enhanced its electrical conductivity and strengthened the chemical interactions with polysulfides toward superior sulfur confinement. Moreover, the carbon coating layer has a hollow spherical architecture that can accelerate electron or ion transportation. Additionally, the Co nanoparticles promote sulfur redox conversion. Benefiting from these synergistic features, the S/Co/TiO2-x@carbon electrode delivers outstanding cycling stability (the capacity decay rate of 0.044% per cycle after 500 cycles) and a superior rate performance (972 mAh g−1 at 2.0C).