Melamine-Sacrificed Pyrolytic Synthesis of Spiderweb-like Nanocages Encapsulated with Catalytic Co Atoms as Cathode for Advanced Li-S Batteries

Due to the high theoretical capacity of 1675 mAh g−1of sulfur, lithium-sulfur (Li-S) batteries can reach a high energy density of 2600 Wh kg−1, which has shown fascinating potential in recent decades. Herein, we report the spiderweb-like nanocage (Co/Mel) as a novel sulfur host with a melamine-sacrificed pyrolysis method. The incorporation of embedded cobalt nanoparticles (Co NPs) in the tips of carbon nanotubes (CNTs) can catalyze polysulfide transformation kinetics. In addition, the nanocages form a conductive three-dimensional spiderweb-like network that facilitates electrolytic penetration and electronic/ionic transportation. Moreover, the porous internal nano-cavities not only improve sulfur loading levels but also provide buffer space for volume expansion during charging and discharging. As a result, the hollow Co/Mel polyhedra with a high content of sulfur (75.5 wt%) displays outstanding electrochemical performance with an initial discharge-specific capacity of 1425.2 mAh g−1at 0.1 C and a low decay rate of only 0.028% after 1000 cycles at 1 C.Keywords:lithium-sulfur batteries;pyrolytic synthesis;zeolite imidazolate framework;spiderweb-like nanocages;catalytic conversion