Facile synthesis of hierarchical Ni7S6 and Co(ii)-doped Ni7S6 flower structures for high-performance supercapacitors

Abstract

A unique 3D flower-like Ni₇S₆ structure was synthesized via a mixed solvothermal method. The as-prepared flower-like Ni₇S₆ structure with abundant active sites demonstrated good supercapacitor performance in an alkaline solution. The pure Ni₇S₆ electrode exhibited high specific capacity (2010 F g⁻¹ at a current density of 1 A g⁻¹), excellent rate performance, and long-term cycling stability owing to its unique structure, and it tolerated fast redox reactions in a harsh alkaline electrolyte. Additionally, to evaluate the Ni₇S₆ electrode for practical applications in energy storage devices, an asymmetric supercapacitor (ASC) device Ni₇S₆//AC (activated carbon) was fabricated, and the Ni₇S₆ electrode prominently enhanced the energy density of the ASC with maximum energy density as well as superior durability with 75.4% capacitance retention after 5000 cycles. For comparison, a designed Co ion-doped Ni₇S₆ (Co_0.7Ni_6.3S₆) flower was also prepared, and the supercapacitor performances were evaluated further. The results showed that the capacitive performance of the pure Ni₇S₆ electrode was superior to the capacitance of the Co(II)-doped Ni₇S₆ electrode at high current densities. Therefore, the flower-like Ni₇S₆ electrode material holds great promise as a potential candidate in high-performance supercapacitor devices.