Electrochemical activation induced phase and structure reconstruction to reveal cobalt sulfide intrinsic energy storage capacity

Transition metal sulfides are considered to be a promising material for energy storage due to their abundant structure and excellent electrical conductivity. However, the neglect of the activation process of these materials in some specific situations may hinder our understanding of the intrinsic mechanism and capacity in the energy storage process. Here, cobalt sulfide is taken as the object of study to reveal the transformation during electrochemical activation. Graphene-loaded cobalt sulfide nanoparticles were prepared by calcination and in situ transformed into defect-rich CoOOH nanosheets by rapid electrochemical activation. Notably, the activation process is inevitable for cobalt sulfide in an alkaline environment under operating conditions, which enables cobalt sulfide to exhibit energy storage capacity. Moreover, other battery-type metal sulfides also undergo activation with similar electrochemical features indicating the universality of this activation process. Meanwhile, the materials exhibit superior performance after sufficient activation. Typically, the activated Co-OH/G exhibits a specific capacity of 511C g(-1) at 1 A g(-1) and capacity retention of 65.9% at 50 A g(-1). More significantly, the new insights and in-depth research of the activation process make it possible to design advanced materials utilizing activation processes.