The development of lithium−sulfur batteries has become an important area of research to meet the growing demand of modern society for energy-storage devices as sulfur cathode is benefited from the excellent theoretical capacity of 1672 mAh g⁻¹, low cost, abundant reserves, and environmental benignity. However, its practical application is strongly impeded by the sluggish kinetics of sulfur redox within aprotic electrolytes and the shuttle effect of soluble intermediate polysulfides. The incompatibility between highly polar polysulfides and conventional carbonaceous conductive substrates is believed to be the main reason for both unfavorable redox activity and polysulfide “flooding”.¹ Here two host materials for sulfur cathodes beyond typical nanocarbon are presented. (1) Nitrogen-doped carbon nanotubes were employed to build sulfur composite cathodes and to examine the heteroatom-doping effect on the sulfur electrochemistry. The electrochemical measurements combined with ab initio calculation validated an enhanced capacity of 1370 mAh g⁻¹ at 0.1 C, over eight-times extended cyclic life, and reduced polarization via only 1.8 % nitrogen incorporation.² (2) The sulfiphilic surface properties of bulk cobalt disulfide (CoS₂) was demonstrated by static adsorption and theoretical calculation. Further hybridization of 15 % CoS₂ with graphene demonstrated a high capacity of 1368 mAh g⁻¹ at 0.5 C, low decay rate of 0.034% over 2000 cycles at 2.0 C, and 10 % increase in energy efficiency. More importantly, the electrocatalytic effect on liquid−liquid polysulfide redox was first verified by assembling symmetric cells.³The two surface-chemistry-initiated design is believed to bring new opportunity to propel the development of advanced sulfur lithium−sulfur batteries as well as other novel energy storage devices.

References:

1. Peng, H.-J.; Zhang, Q. Angew. Chem. Int. Ed. 2015, 54, 11018–11020
2. Peng, H.-J.; Hou, H.-Z.; et al. Adv. Mater. Interfaces 2014, 1, 1400227
3. Yuan, Z.; Peng, H.-J.; et al. Nano Lett. 2016, doi: 10.1021/acs.nanolett.5b04166