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 (Co0.7Ni6.3S6) 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.