Selective combination of highly porous hollow structured bimetallic spinel oxides with improved redox chemistry for electrochemical hybrid capacitor

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Highly porous hollow/core-shell nanostructures with controlled shapes and sizes have fascinated great importance in the development of high-performance energy storage devices. The well-controlled porous nanostructures with larger surface area could provide better electrochemical behavior owing to rapid diffusion of electrolyte ions into their interiors and demonstrate maximum charge storage capacity compared to their solid counterparts. Herein, we designed highly porous spinel structured CoMn2O4 hollow nanospheres (CMO HNSs) and hierarchical porous MnCo2O4 nanoflowers (MCO NFs) with controlled morphologies using ethylene glycol as a mediated solvent via a simple and eco-friendly wet chemical method. The prepared materials revelaed dominant battery-type behavior with excellent electrochemical performance in aqueous alkaline electrolyte. With the synergistic morphological features, the designed construction of CMO HNSs exhibited a maximum specific capacity of 168 mA h g−1 at current density of 1 A g−1 with superior cycling stability (∼90% at 6 A g−1) which were comparatively higher than the MCO NFs. Moreover, a pouch-like electrochemical hybrid capacitor was fabricated with CMO HNSs and activated carbon, which delivered a maximum energy density of 26.8 W h kg−1 and power density of 9816 W kg−1 with longer cycling durability. By utilizing higher energy storage performance, the fabricated device effectively powered up various portable electronic devices.