Self-supported Ni3S2/NiCo2O4 core-shell flakes-arrays on Ni foam for enhanced charge storage properties

Abstract Herein, we design and prepare Ni 3 S 2 /NiCo 2 O 4 arrays on Ni foam with core-shell flakes structure as charge-storage materials. In this synthetic strategy, NiCo 2 O 4 flakes are firstly grown on Ni foam substrate through simple hydrothermal process, and then ultrathin Ni 3 S 2 nanoflakes are electrodeposited into scaffold of NiCo 2 O 4 arrays. Those nanoflakes supported with each other can form a three-dimensional porous and interconnected structure, which afford more active sites and ion transfer channels for redox reaction. As expected, Ni 3 S 2 /NiCo 2 O 4 arrays show excellent charge-storage properties in electrochemical energy storage, including high specific capacity of 1201 C g -1 (3.46 C cm -2 ) at 1 mA cm -2 , which far larger than those of pure NiCo 2 O 4 (572 C g -1 , 0.86 C cm -2 ) and Ni 3 S 2 (612 C g -1 , 0.98 C cm -2 ). Meanwhile, Ni 3 S 2 /NiCo 2 O 4 arrays show a good rate capability of 742 C g -1 at 60 mA cm -2 . Furthermore, hybrid device is fabricated using Ni 3 S 2 /NiCo 2 O 4 arrays (positive electrode) and graphene on Ni foam (negative electrode). This device can deliver high energy density of 47.62 Wh kg -1 , indicating a good application ability of Ni 3 S 2 /NiCo 2 O 4 arrays. The excellent charge-storage performance of Ni 3 S 2 /NiCo 2 O 4 arrays is attributed to the core-shell structure of flakes arrays and synergistic effects of two components.