Constructing Hollow Ni0.2Co0.8S@rGO Composites at Low Temperature Conditions as Anode Material for Lithium‐Ion batteries

Abstract Due to their high theoretical capacities, metal sulfides have been considered as promising electrode materials for lithium‐ion batteries (LIBs). Heavy‐duty applications of metal sulfides for LIBs, however, are still restricted by the unavoidable volume change, resulting in poor rate capability and cycling stability. In this work, a Ni−Co‐ZIF derived Ni 0.2 Co 0.8 S hollow nanocage@reduced graphene oxide (Ni 0.2 Co 0.8 S@rGO) composite was fabricated through facile self‐assembly followed by freeze‐drying. The highly porous architecture of Ni 0.2 Co 0.8 S hollow nanocages wrapped by flexible reduced graphene oxide (rGO) is shown to not only validly inhibit the huge volume expansion during repeated charge/discharge cycling, but also accelerate lithium‐ion and electron transport through the 3D rGO network. The as‐obtained Ni 0.2 Co 0.8 S@rGO exhibits excellent electrochemical performance with a high specific capacity of 1585 mA h g −1 after 250 cycles at a current density of 1 A g −1 . It is shown that the increasing reversible capacity during cycling can be attributed to the electrochemical activation of porous Ni 0.2 Co 0.8 S‐2.5@rGO, the pseudocapacitive behavior, and the highly reversible formation/decomposition of the solid electrolyte interface layer during lithiation/de‐lithiation. The sulfidation and reduction syntheses were operated at a relative low temperature of 90 °C, which is beneficial to inherit the unique morphology of precursor.