A hollow urchin-like metal–organic framework with Ni–O-cluster SBUs as a promising electrode for an alkaline battery–supercapacitor device

Abstract

A hollow urchin-like Ni-based MOF material (named NiPSC) with long tentacles has been synthesized and directly utilized as an active electrode material in supercapacitors. By virtue of multi-centered Ni-oxo SBU clusters and a large d-spacing distance, the pristine NiPSC electrode delivers superior electrochemical performance, including high specific capacity, good rate capability and outstanding cycling stability even under the erosion of an alkaline electrolyte. Moreover, the NiPSC//AC device with NiPSC as the positive electrode and active carbon (AC) as the negative electrode exhibits an excellent capacitance retention of 82.8% after 3000 cycles with a window voltage of 1.7 V, a maximum energy-density value of 28.81 W h kg⁻¹ at 425 W kg⁻¹, and potential practicability (two cells can power four LED bulbs for 10 min). Our results suggest that the strategy of modifying the interior structures of MOFs through introducing multiple redox-active sites and adjusting the crystal-lattice distance could effectively improve the performance of the as-obtained materials in supercapacitors.