NiCoSe4 nanoparticles derived from nickelâ€"cobalt Prussian blue analogues on N-doped reduced graphene oxide for high-performance asymmetric supercapacitors.

Synthesis of NiHCCo precursors via simple co-precipitation and nickelâ€"cobalt tetraselenide composites grown on nitrogen-doped reduced graphene oxide (NiCoSe4/N-rGO) were fabricated using solvothermal method. The introduction of N-rGO used as a template effectively prevented agglomeration of NiCoSe4 nanoparticles and provided more active sites, which greatly increased the electrochemical and electrical conductivity for NiCoSe4/N-rGO. NiCoSe4/N-rGO-20 presents a remarkably elevated specific capacity of 120 mA h gâˆ'1 under current density of 1 A gâˆ'1. NiCoSe4/N-rGO-20 demonstrates an excellent cycle life and achieves a remarkable 83% retention rate over 3000 cycles with 10 A gâˆ'1. NiCoSe4/N-rGO-20//N-rGO asymmetric supercapacitor was constructed based on the NiCoSe4/N-rGO-20 as an anode, N-rGO as cathode by using 2 mol lâˆ'1 KOH as an electrolyte. NiCoSe4/N-rGO-20//N-rGO ASC demonstrates an ultra-big energy density of 14 Wh kgâˆ'1 and good circulation stability in the power density of 902 W kgâˆ'1. It is doubled in comparison to the NiCoSe4/N-rGO-20//rGO asymmetric supercapacitor (7 Wh kgâˆ'1). The NiCoSe4/N-rGO-20//N-rGO ASC capacity retention is still up to 93% over 5000 cycles (5 A gâˆ'1). The results reveal that this device would be a prospective cathode material of supercapacitors in actual applications. [ABSTRACT FROM AUTHOR]