Construction of thickness-controllable bimetallic sulfides/reduced graphene oxide as a binder-free positive electrode for hybrid supercapacitors

Devices for electrochemical energy storage with exceptional capacitance and rate performance, outstanding energy density, simple fabrication, long-term stability, and remarkable reversibility have always been in high demand. Herein, a high-performance binder-free electrode (3D NiCuS/rGO) was fabricated as a supercapacitor by a simple electrodeposition process on a Ni foam (NF) surface. The thickness of the deposited materials on the NF surface was adjusted by applying a low cycle number of cyclic voltammetry (5 cycles) which produced a thin layer and thus enabled the easier penetration of electrolytes to promote electron and charge transfer. The NiCuS was anchored by graphene layers producing nicely integrated materials leading to a higher electroconductivity and a larger surface area electrode. The as-fabricated electrode displayed a high specific capacitance (2211.029 F g^-1 at 5 mV s^-1). The NiCuS/rGO/NF//active carbon device can achieve a stable voltage window of 1.5 V with a highly specific capacitance of 84.3 F g^-1 at a current density of 1 A g^-1. At a power density of 749 W kg^-1, a satisfactory energy density of 26.3 W h kg^-1 was achieved, with outstanding coulombic efficiency of 100% and an admirable life span of 96.2% after 10 000 GCD cycles suggesting the significant potential of the as-prepared materials for practical supercapacitors.