The different electrochemical performance of nickel–cobalt sulfide and its formation mechanism of honeycomb-like structure

Various double-solvent systems, including EG–IPA, glycerol–IPA, EG–methanol and EG–ethanol etc., were used to fabricate nickel–cobalt sulfide (NCS). Their products showed different structure with granular-, hollow sphere-, honeycomb-, irregular sphere-like microstructures and so on. The electrochemical performances of these samples were investigated by CV and GCD measurements. The results indicate that at 1A/g, their specific capacitances are 912, 980, 1464, 1072, 1130, 1108, 1006 and 866 F/g, respectively, among which honeycomb-like structure has the best performance. The best sample also shows excellent charge–discharge performance, that is, it still retains more than 88% of the initial capacity after 2000 cycles. Furthermore, the formation mechanism of the pores in the honeycomb structure was studied in detail. Therefore, a special experiment was designed to reveal the cause of the pore formation. This study is of great significance for the design of transition metal compounds with excellent electrochemical properties.