Résumé
Spinel metal oxides are extensively studied for supercapacitors (SCs) in alkaline electrolytes, where charge storage capacity is limited by surface site availability due to surface reconstruction forming metal hydroxides/oxyhydroxides. The use of an acidic medium, which can boost the charge storage capacity of spinel oxides offering an additional channel of intercalation-deintercalation of protons, is underexplored. Moreover, the impact of chemical compositions and the cationic distributions is crucial on the electrocatalysis performance of spinel oxides, however, such a correlation is first time reported for charge storage properties of spinel ferrite NiFe2O4 nanoparticles (NFO NPs). Besides, a low-cost and scalable synthesis of NFO NPs involving the thermal decomposition of Ni-Fe glycolate, followed by controlled air-calcination is reported. Thus crafted NFO NPs-based device shows impressive specific capacitance (2112 F g(-1) at 10 A g(-1)) in half-cell configuration. A flexible all-solid-state asymmetric device (full-cell) configuration depicts impressive energy density (20.7 Wh kg(-1)), power density (4000 W kg(-1)), gravimetric capacitance (140 F g(-1) at 2 A g(-1)), and retention of its performance (approximate to 75% after 10,000 charging/discharging cycles). The results depict a new insight toward the tuning of electronic and charge storage properties in NFO, which otherwise are predominately attributed to only the crystallite size and morphological effects.