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

Abstract

Herein, we design and prepare Ni3S2/NiCo2O4 arrays on Ni foam with core-shell flakes structure as charge-storage materials. In this synthetic strategy, NiCo2O4 flakes are firstly grown on Ni foam substrate through simple hydrothermal process, and then ultrathin Ni3S2 nanoflakes are electrodeposited into scaffold of NiCo2O4 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, Ni3S2/NiCo2O4 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 NiCo2O4(572 C g−1, 0.86 C cm−2) and Ni3S2 (612 C g−1, 0.98 C cm−2). Meanwhile, Ni3S2/NiCo2O4 arrays show a good rate capability of 742 C g−1 at 60 mA cm−2. Furthermore, hybrid device is fabricated using Ni3S2/NiCo2O4 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 Ni3S2/NiCo2O4 arrays. The excellent charge-storage performance of Ni3S2/NiCo2O4 arrays is attributed to the core-shell structure of flakes arrays and synergistic effects of two components.