Layered double hydroxide based on ZnCo@NiCo- nano-architecture on 3D graphene scaffold as an efficient pseudocapacitor

Herein, we report a simple one pot all hydrothermal synthesis route to grow nano structure of zinc-cobalt (Zn-Co) @ nickel-cobalt (Ni-Co) layered double hydroxides through oriented attachment growth with ultrathin nanosheets on 3D graphene foam using no additives or oxidants. The pseudocapacitor electrode based on Zn-Co@Ni-Co layered double hydroxides display an enhanced areal capacitance (7485 mFcm⁻², at 5 mVs⁻¹) and energy density (1202 mWhcm⁻², at 15 mAcm⁻²) compared to pristine Zn-Co layered double hydroxides, with a greater cycling stability of 108% after 5000 charging-discharging cycles. We fabricate an all solid state symmetrical supercapacitor device with G-Zn-Co@Ni-Co//G-Zn-Co@Ni-Co layered double hydroxides that exhibits an areal capacitance of 1278 mFcm⁻², at 10 mVs⁻¹ and energy density of 171 mWhcm⁻², at 2.5 mAcm⁻². The credit of superior performance of these pseudocapacitor electrodes is to the easy access of electrolyte to the nanosheets, the conductivity enhancement by 3D graphene foam scaffold and the synergistic effect due to the composite structure of the Zn-Co@Ni-Co layered double hydroxides.