Hierarchically porous Ni monolith@branch-structured NiCo2O4 for high   energy density supercapacitors
  NiCo2O4 of varying nanostrucutures ranging from nanowires, nanoplates to nano-plates@nanowires were successfully grown on microporous (MP) Ni foams via one-step hydrothermal process. The investigation of electrochemical capacitance favors Ni-Co2O4 of nanoplates@nanowires microstructures which possesses specific capacitance of 1380.3 F/g and 1033F/g at 5A/g and 50A/g respectively and 86.7% capacitance re-tention after 5000 cycles at 30A/g. The relationship between morphology and specific capacitance was further explored by the model of surface roughness factor (RF), which is indicative of the active electrode-electrolyte interface areas. The RF of porous Ni@NiCo2O4 was remarkably improved by employing hierarchically porous (HP) Ni monoliths as substrates, which illustrates the model of high energy density (12.6 F/cm2) electrodes for super-capacitors. 
Qin Guo, Mengjie Xu, Rongjun Xu, Ying Zhao, Boyun Huang
cond-mat.mtrl-sci