Cobalt-doped zinc manganese oxide porous nanocubes with controlled morphology as positive electrode for hybrid supercapacitors

Abstract

Rationally designed porous structured electrode materials have attracted significant potential interest in hybrid supercapacitors owing to their more predominate surface area and endow the superior energy storage capability. The synthesis strategy of these multifunctional porous structures is more desirable and still inferior. Herein, we synthesized novel ZnMn2O4 (ZMO) or cobalt (Co)-doped ZMO porous nanocubes (PNCs) by a facile solvothermal method, followed by calcination in air. The NH4F played an important role as a template in the formation of nanocubes morphology and detailed growth process was investigated. Impressively, with the incorporation of different molar concentrations of Co ions into pristine ZMO, the electrochemical performance was enhanced and the capacitance values were significantly increased due to the porosity and multi-metal ions synergistic effect. The pristine ZMO and the optimized Co-doped ZMO PNCs exhibited maximum specific capacitance values of ∼267 and ∼1196 F g−1, respectively, at 1 A g−1 of current density. The optimized ZMO:5Co PNCs electrode exhibited more than 4 times in its specific capacitance value with respect to the pristine ZMO PNCs at a constant current density (1 A g−1), and it also showed excellent cycling performance (∼85.5%) at higher current density (7 A g−1). Furthermore, a hybrid supercapacitor (HSC) device was made by utilizing ZMO:5Co PNCs (positive) and activated carbon (negative) electrodes, exhibiting a maximum specific capacitance of ∼68 F g−1 at 1 A g−1 of current density and a high energy density of 27.38 W h kg−1 at a high power density of 1059 W kg−1 within a potential window of 1.45 V. The HSC device also showed excellent cycling stability with ∼80.5% of capacitance retention after performing the 4000 cycles.