Three dimensional hierarchical porous nickel cobalt layered double hydroxides (LDHs) and nitrogen doped activated biocarbon composites for high-performance asymmetric supercapacitor

Abstract

Nitrogen-doped activated biocarbon (AC) and nickel-cobalt layered double hydroxides (LDHs) composites (NixCo1−x LDH/AC) are prepared by solvothermal method at various Ni/Co molar ratios. 3D nanoflowers composed of LDH nanosheets are spontaneously grown on the surface of AC from bio-waste, providing a suitable structure for the diffusion and transport of electrolyte ions. Ni0.5Co0.5LDH/AC composite electrode has high specific capacitance of 947 F g−1 at the current density of 1 A g−1, which could be explained by the synergistic effect of LDHs and AC. Furthermore, symmetric coin-cell AC//Ni0.5Co0.5 LDH/AC supercapacitor is assembled using Ni0.5Co0.5 LDH/AC composite as the cathode, and the pristine AC as the anode. Within 1.6 V voltage range, the supercapacitor device shows a maximum capacitance values (Csc) of 112 F g−1 at 1 A g−1. The developed asymmetric supercapacitor exhibits excellent rate performance and good cycle stability reflected through the maintenance of 80% of the initial Csc after 5000 consecutive cycles. Moreover, high energy density (39.7 Wh kg−1) is observed at low power density of 0.8 kW kg−1, and maintained at relatively high value (22.2 Wh kg−1) at high power density (16 kW kg−1). All these data indicate the potential applicability of AC//Ni0.5Co0.5 LDH/AC asymmetric supercapacitor for energy storage.