Co-Ni Binary-Metal Oxide Coated with Porous Carbon Derived from Metal-Organic Framework as Host of Nano-Sulfur for Lithium-Sulfur Batteries

Lithium-sulfur battery is considered as a promising energy storage system because of its high energy density. The specific capacity and cycling stability of sulfur cathode, however, are impeded by intrinsic poor electrical conductivity of sulfur and dissolution of polysulfides intermediates. Herein, we demonstrate a novel strategy to overcome the two obstacles by designing a bimetallic-organic-framework-derived nano-sulfur host consisted of porous graphitic carbon and bimetallic cobalt-nickel oxides (C/NiCo2O4), in which porous carbon and NiCo2O4 not only entrapping the polysulfides effectively through physical and chemical entrapment capability, but also serving as a highly conductive matrix for sulfur. With a sulfur content of 68.9% in the composite, the composite cathode delivered a specific capacity of 977mAhg(-1) and maintained 673mAhg(-1) at 0.5C over 500 cycles. Besides, the binding mechanism between NiCo2O4 and polysulfides has been explored by ex situ XRD and density functional theory(DFT)simulation. This work may provide a feasible strategy to improve the performance of lithium-sulfur battery.