High retention supercapacitors using carbon nanomaterials/iron oxide/nickel-iron layered double hydroxides as electrodes

•rGO-FeO-CNT-700 hierarchical structure were prepared by using oyster shell powder as the promoter for forming and grew CNTs on the rGO surface.•rGO-FeO-CNT-700-NiFeLDH-60 electrode shows an excellent capacitance of 411.9 F g-1 tested at 5 mV s-1.•The good retention rate of 102.2% was attained after 5000 charge/discharged cycles.•The asymmetric supercapacitor delivers a high energy density.