Controlled synthesis of Ni_0.85Se microstructures with different morphologies and their morphology-dependent electrochemical supercapacitor properties

The research of cheap, earth-abundant and efficient electrode material is of significance for advanced supercapitors. Here we report a simple and cost-effective strategy for synthesis of Ni_0.85Se via hydrothermal method. A systematic study of the solvent dependent morphological modification and its subsequent influence on supercapitors performance have been investigated. When evaluated as electrode material in supercapacitor, the as-fabricated flower-like Ni_0.85Se electrode shows superior electrochemical performance with excellent rate capability and long cycle life. Besides, the energy storage behavior of flower-like Ni_0.85Se was investigated in an asymmetric supercapacitor configuration. The as-assembled Ni_0.85Se//graphene hybrid supercapacitor showed a specific capacitance of 103.4 F g⁻¹ at 1 A g⁻¹ and cycle performance of 90.6% after 10 000 uninterrupted cycles at a high current density of 8 A g⁻¹. Furthermore, the maximum energy density of 32.3 Wh kg⁻¹ and power density of 1.5 kW kg⁻¹ were obtained. The high specific capacitance and good cyclic stability as well as high energy/power density of the device make it a promising supercapacitor for the practical applications. Moreover, this work also provides a straightforward and effective approach to synthesize selenide-based electrode material in high performance energy storage devices.