One-step co-precipitated β-Ni(OH)2 at different ratios of Ni/2-methylimidazole and its energy storage behaviour

In this study, a series of Ni-based Zeolitic Imidazolate Framework (ZIF) is successfully co-precipitated at room temperature with different ratios of nickel (II) nitrate hexahydrate (Ni(NO 3 ) 2 ⋅6H 2 O) to 2-methylimidazole (mIM) at different ratios of 3:10, 1:1, and 10:3, denoted as Ni-ZIF-1, Ni-ZIF-2, and Ni-ZIF-3. The morphology, elemental, and structural investigation of Ni-ZIFs are carried out using field emission scanning electron microscopy (FESEM), energy-dispersive X-Ray spectroscopy (EDX), Fourier transform infrared (FTIR) spectroscopy, and X-ray diffraction (XRD). The electrochemical performance reveals that the Ni-ZIF-3 successfully delivered the highest specific capacitance of 433 F g −1 at current density of 0.25 A g −1 . It is important to note that when Ni-ZIF-3 is used in carbon asymmetric supercapacitor (ASC), the specific capacitance of 85 F g −1 is achieved at a current density of 0.25 A g −1 , whilst maintaining outstanding cycling stability of 93% after 1500 cycles at reversible current density from 0.5 A g −1 until 1.0 A g −1 . A little decay during the cycle test demonstrates that the device is capable of offering durable devices with low internal resistance. Graphic abstract