Cobalt-loaded three-dimensional ordered Ta/N-doped TiO2 framework as conductive multi-functional host for lithium-sulfur battery

Abstract

The low electrical conductivity of sulfur and severe shuttling effect of lithium polysulfides (LiPSs) have hindered the practical application of lithium-sulfur (Li-S) batteries. In this work, a conductive Ta/N co-doped TiO2 framework featured with three-dimensional ordered macroporous (3DOM) structure embedded with ZIF-67 derived Co-anchored N-doped carbon (Co-NC) is synthesized as efficient sulfur host material in Li-S batteries. The 3DOM Ta/N-TiO2 backbone has good structural stability, which benefits the electrolyte penetration and sulfur accommodation. Meanwhile, the Ta/N co-doping not only improves the conductivity of TiO2, but also strengthens the adsorption of LiPSs. In addition, the embedded Co-NC increases the active site of 3DOM skeleton towards LiPSs conversion, facilitates the diffusion of Li+ ion, and at the same time provides additional microspores for sulfur confinement. Attributed to these features, the sulfur electrode based on 3DOM Ta/N-TiO2@Co-NC achieves excellent electrochemical performance. The S/3DOM Ta/N-TiO2@Co-NC cell maintains a discharge capacity of 789.2 mAh g−1 after 500 cycles at 1C with a low decay rate of 0.06 % per cycle. Additionally, an initial area capacity of 5.67 mAh cm−2 is obtained under areal sulfur loading of 6.55 mg cm−2. This multistage porous sulfur cathode design has the potential to expedite the development of feasible Li-S battery.