Structural rearrangement by Ni,Cr doping in zinc cobaltite and its influence on supercapacitance

Transitional metal oxides are prevalent in the energy storage devices due to their remarkable electrochemical activity and charge storage capability. In this study, a spinel structured zinc cobaltite (ZnCo₂O₄) is doped with Ni and Cr to form a novel (Ni,Cr:ZnCo₂O₄) electrode material towards supercapacitor (SC) applications. Dopants served as a conductivity booster, particle size reducer and active sites provider benefitting the electrochemical activity. Comparatively, the doped sample delivered a higher capacitance value of 575 Fg^-1 in the potential range of 0–0.6V with 1 M KOH solution as an electrolyte which is higher than that of the pristine material and better cyclic stability is improved from 82.2% to 90.24% for 2000 cycles. The specific capacitance value of 30 Fg^-1 and 73 Fg^-1 at 0.75 Ag^-1 is achieved for the fabricated asymmetric supercapacitor device with Ni,Cr:ZnCo₂O₄ using Cu foil and Ni foam as current collector respectively. The device assembled with doped sample using Ni foam current collector has an energy density of 16.3 WhKg^?1 and a power density of 0.9 KWKg^?1 superseding the performance of the devices constructed with the pristine ZnCo₂O_4. The performance of Ni and Cr doped spinel structured zinc cobaltite device indicates a notable progress towards the direction of better performance supercapacitor applications.