Controllable synthesis of porous NiCo2O4/NiO/Co3O4 nanoflowers for asymmetric all-solid-state supercapacitors.

Highlights • Porous NiCo 2 O 4 /NiO/Co 3 O 4 nanoflowers (NCNs) are prepared by adding oxalic acid. • NCNs-0.1 possess optimal distribution of micro-mesopores. • NCNs-0.1 electrodes deliver an enhanced specific capacitance of 1693F g−1. • 88% capacitance can be retained after 6000 cycles. • Excellent energy densities of 43.02 Wh kg−1 and power densities of 820.29 W kg−1. Abstract The rational design of micro-mesopores is a hugely challenging for porous metal-based nanomaterials. Here oxalic acid (H 2 C 2 O 4) as control agent is proposed for the first time to prepare 3D optimal micro-mesoporous NiCo 2 O 4 /NiO/Co 3 O 4 nanoflowers (NCNs). Theoretical and experimental analyses demonstrate NCNs-0.1 which are prepared by adding 0.1 g H 2 C 2 O 4 possess optimal distribution of micro-mesopores. The optimal structure creates abundant active sites and fluent ionic channels. Beneficially, NCNs-0.1 electrodes deliver an enhanced specific capacitance of 1693F g−1 at 1 A g−1 and outstanding cyclic stability (88% capacitance retention after 6000 cycles). Further, the assembled NCNs-0.1//AC capacitor achieves excellent energy densities of 43.02 Wh kg−1 at power densities of 820.29 W kg−1. The current NCNs-0.1 confirms a practicable method to optimize the electrochemical performances of supercapacitors by utilizing H 2 C 2 O 4 to construct 3D optimal micro-mesoporous nanoflower architectures. [ABSTRACT FROM AUTHOR]