Development of nanohybrids based on porous spinel MCo2O4 (M = Zn, Cu, Ni and Mn)/reduced graphene oxide/carbon nanotube as promising electrodes for high performance energy storage devices

Designing advanced hybrid supercapacitors (SCs) with high energy density and long-term cycling stability remains a significant hurdle. Herein, we developed a hierarchal porous spinel MCo2O4 (M = Zn, Cu, Ni and Mn)/ reduced graphene oxide (RGO)/carbon nanotube (CNT) nanocomposite as a binder-free SC electrode. The effects of cation substitution and carbon nanomaterials in the content of Co3O4 electrodes and its electrochemical performances are thoroughly studied. The highest activity observed for a SC constructed with NiCo2O4/RGO/CNT electrode attained is 890 Fg(-1) at 1 Ag-1 and capacitance retention of 91% over 4000 cycles which is greater than 205 Fg(-1) and 80% of pristine Co3O4 in 2 M KOH. Furthermore, an asymmetric SC is assembled with NiCo2O4/RGO/CNT electrode exhibits an excellent energy density of 34.5 Whkg(-1) at a power density of 799 VVkg(-1), high specific capacitance (94.2 Fg(-1) at 1 Ag-1) and outstanding cyclic stability (9.8% loss over 5000 cycles) at 1.6 V. These experimental findings may open new perspectives for the design of future competitive hybrid energy storage devices.