Multilayer NiMn layered double hydroxide nanosheets covered porous Co3O4 nanowire arrays with hierarchical structure for high-performance supercapacitors

The hierarchical nanostructure hybrids of porous Co3O4 nanowires coated NiMn layered double hydroxide nanosheets array on Ni foams (Co3O4@NiMn-LDH/Ni) are designed and prepared via the two-step hydrothermal reactions with a combination of annealing process. The Co3O4 nanowires can be utilized as backbone to grow the NiMn-layered double hydroxide (NiMn-LDH) nanosheets, which provide a large surface area and leading to the enhanced capacitive performance owing to the effective ion/electron diffusion rates. The areal capacitance of the as-prepared Co3O4@NiMn-LDH/Ni electrode reaches 19.7 F cm−2 (5419.7 F g−1) at 2 mA cm−2 (0.56 A g−1). Moreover, a high capacitance retention (93.25% of capacitance maintained after 6000 cycles) and a low internal resistance Rs (0.62 Ω) can be acquired. Additionally, an all-solid-state asymmetric supercapacitor (Co3O4@NiMn-LDH/Ni//AC ASC) based on the Co3O4@NiMn-LDH/Ni as positive electrode and activated carbon (AC) as negative electrode is successfully obtained. The Co3O4@NiMn-LDH/Ni//AC ASC shows a high energy density of 47.15 Wh kg−1 at 376 W kg−1. Additionally, a LED can be lit up for 12 min when three ASCs are connected in series. Therefore, this novel Co3O4@NiMn-LDH/Ni with outstanding electrochemical performance should envision potential practical applications in high energy storage appliances.