3D hybrid of Co9S8 and N-doped carbon hollow spheres as effective hosts for Li-S batteries.

Lithium-sulfur (Li-S) batteries as a new generation of high energy batteries, with low cost and environmentally friendly, have a broad application prospects. While the poor conductivity of sulfur, the volume effect and 'shuttle effect' during charge and discharge, and slow redox kinetics of polysulfide intermediates still limit the practical application. To solve these problems, we synthesize a valid 3D hybrid material (Co9S8@N-CHS) of nanosized Co9S8 evenly distributed on N-doped carbon hollow spheres with strong chemical coupling by in situ carbonization of Co(NO3)2@resorcinol/formaldehyde and sulfidation. It presents a high electronic conductivity, absorbing chemical adsorption capability to polysulfides and can catalyze the sulfur redox processes. Compared with S/AC and S/N-CHS electrodes, S/Co9S8@N-CHS electrodes achieve an excellent initial discharge specific capacity of 1337 mAh g-1 at 0.1 C and a long cycle life with an ultralow capacity decay of 0.027% per cycle over 1000 cycles at 1.0 C and the coulombic efficiency is above 99%. Consequently, it is an effective sulfur host material for high performance Li-S batteries.