NiCo2O4 with unique 3D miniature sea urchins as binder-free electrode for high performance asymmetric supercapacitor

Abstract

• NiCo 2 O 4 /NF with unique 3D miniature sea urchins growing on the first layer with nanowire arrays on nickel foam was prepared. • NiCo 2 O 4 /NF shows pseudocapacitive properties with a specific capacitance of 2010F g −1 at a current density of 1 A g −1 . • NiCo 2 O 4 /NF//AC exhibits outstanding cycling stability. • NiCo 2 O 4 /NF//AC exhibits a high energy density of 37.4 Wh kg −1 at 400 W kg −1 . Binder-free bimetallic oxides, especially NiCo 2 O 4 , are important electrode materials for asymmetric supercapacitors (ASCs), and their structural characteristics have a profound effect on the electrochemical performance. Herein, mesoporous NiCo 2 O 4 with unique double layer structure formed by 3D miniature sea urchins growing on the first layer with nanowire arrays on nickel foam (NiCo 2 O 4 /NF) are prepared. The prepared NiCo 2 O 4 can be used as an electrode without adding conductive agent and binder. Under different hydrothermal time (NCO/NF-x, x = 6, 8, 10 and 12 h), NCO/NF-10 shows the largest specific surface area of 83 m 2 g −1 and the highest specific capacitance of 2010F g −1 at 1 A g −1 . The capacitance retention rate of the asymmetric supercapacitor assembled by NCO/NF-10 with activated carbon (AC) can reach 87% after 4500 cycles, and the maximum energy density is 37.4 Wh Kg −1 at a power density of 400 W Kg −1 .