Sulfide with Oxygen-Rich Carbon Network for Good Lithium-Storage Kinetics.

Transition metal sulfides are of great interest as electrode material for alkali metal-ion batteries due to their high theoretical capacity. However, sluggish ion migration and electron transfer kinetics lead to poor cycling stability and rate performance, which hinders their practical applications. Herein, we develop a two-step localized carbonization and sulfurization method to construct a CoS2 composite material (CoS2@CNTs@C) from an in situ integrated zeolitic imidazolate framework (ZIF-67) and multiwalled carbon nanotube precursor (ZIF-67@CNTs). The as-prepared CoS2@CNTs@C composites with a nanoscale carbon skeleton inherit a large specific surface area and suitable nanopore size distribution from ZIF-67 and incredibly abundant oxygenated functional groups from CNTs. The theoretical calculation and material characterization demonstrate that the oxygenated functional groups on the porous carbon networks accelerate lithium-ion diffusion and electron transfer and especially electrocatalyze the progressive conversion of Li2S6 to the final product Li2S. Meanwhile, the three-dimensional conductive network guarantees the conductive and structural stability of CoS2@CNTs@C during the repeated lithium-storage process. Therefore, the CoS2@CNTs@C electrode material can deliver an initial discharge capacity of 1282.3 mA h g-1 at 200 mA g-1 with a high Coulombic efficiency of 93.5% and a reversible capacity of 558.8 mA h g-1 at 2000 mA g-1 in 600 cycles with a high capacity retention of 96.1%.