Carbon-layer encapsulated MOF-derived CoS2 for enhanced sodium ion storage

Abstract

Transition metal sulfides are widely used in sodium-ion batteries due to their high specific capacity. However, they encounter the issue of polysulfide shuttling. To tackle this problem, we synthesized ZIF-67-derived CoS2 (C@ZIF-CoS2) through coating with a conductive carbon layer. The coated carbon layer mitigates the structural alterations of CoS2 during the charging and discharging processes. Additionally, the carbon layer prevents the shuttling of polysulfides. As a result, the obtained C@ZIF-CoS2 demonstrates outstanding cycling stability. Even after 300 cycles at a current density of 0.1 A g-1, it still retains a reversible specific capacity of 262.5 mAh g-1, with a capacity retention rate of 93.1%.