Double role of CoO Co4N hetero-nanocages as sulfur host for lithium-sulfur batteries

Lithium-sulfur batteries (LiSBs) are widely deemed as the most promising energy storage devices to substitute for traditional Li-ion batteries. However, its wide application is impeded by the soluble lithium polysulfides (LiPSs), which is called the shuttle effect, and the irregular distribution of final product Li2S. Herein, based on the interfaces engineering, CoOCo4N hetero-nanocages are used as the sulfur host for LiSBs. Taking advantage of the polarity of CoO with the conductivity of Co4N, CoOCo4N nanocages not only can provide large void space for sulfur volume fluctuation, but also can adsorb polysulfides and simultaneously regulate the nucleation of solid Li2S by the ‘trapping-diffusion-conversion’ mechanism, which significantly enhances the redox kinetic of LiSBs and the utilization of active materials. Eventually, LiSBs with CoOCo4N nanocages host exhibit higher rate capacity (737 mAh·g−1 at 2 C) and cycling stability (662 mAh·g−1 at 1 C after 350 cycles). Even when the areal sulfur loading is as high as 3.0 mg cm−2, a high capacity of 713 mAh·g−1 can still be achieved after 100 cycles at 0.2 C. This host with sufficient polar-conductive interfaces expands ‘trapping-diffusion-conversion’ concept for the design of fast kinetic and high performance LSBs.