Design and synthesis of NiCo2O4 wire-shaped electrode based on nickel wire with porous foam structure for wire-shaped hybrid supercapacitors

The wire-shaped supercapacitors (SCs) have been widely concerned in wearable electronic devices because of their portability. However, it is still a challenge to prepare wire-like current collectors and high-performance active materials for wire-shaped SCs. Herein, we designed a nickel wire with a three-dimensional porous foam structure, which can be used as the wire-like current collector for loading active materials. And then self-supporting NiCo2O4 nanosheet arrays were electrodeposited into the as-prepared nickel wire without any binder. Moreover, the wire-shaped NiCo2O4@Ni electrode shows excellent electrochemical performance with specific capacitance of 1396.4 F g-1, high rate performance and good cycling stability maintaining capacitance retention of 84.3% after 5000 charge/discharge cycles. In addition, the NiCo2O4@Ni//N-RGO@Ni wire-shaped SCs device has a high specific energy of 25.0 Wh kg-1. Therefore, nickel wire with a three-dimensional porous foam structure can be used as a promising wire-like current collector, and self-supporting NiCo2O4 nanosheet arrays have great potential in wire-shaped supercapacitor devices. This work may provide a new solution for the design of wire-shaped current collectors and electrodes.