Thermally driven high-rate intercalated pseudocapacitance of flower-like architecture of ultrathin few layered δ-MnO₂ nanosheets on carbon nano-onions

The layered two-dimensional (L2D) nanostructures are greatly favorable electrode materials in electrochemical energy storage as a consequence of enhanced specific surface area and effective intercalation of ions. However, the realizations of uniform L2D structure with appropriate van der Waals gap and its three-dimensional architecture of a few-layered association enhance the accommodation of ions for superior supercapacitor. Temperature driven boost in the storage by compensating minor life span is highly noteworthy. Herein, we report a fascinating 3D architecture composed of L2D δ-MnO₂ nanosheets decorated on carbon nano-onion (CNO) by a cost-effective, template-free, low-temperature chemical route. The temperature-driven electrochemical kinematics exhibits efficient charge storage capacity via intercalated pseudocapacitance. The specific capacitance was boosted from 147 F·g⁻¹ to 321 F·g⁻¹ with increasing temperature from 4 to 70 °C at 2 mV·s⁻¹. Nevertheless, merely 25% stability retention has been forfeited up to 6000 cycles at high current density (5 A·g⁻¹). Furthermore, the flexible asymmetric device (FAD) demonstrates a high operating voltage of 1.8 V and superior bendability via retention of 97% capacitance with the bending angles from 0° to 180°. The superior energy density of 49.5 Wh kg⁻¹ and excellent stability of 89% up to 10 000 cycles are figures of merit of L2D δ-MnO₂ nanosheets decorated on carbon nano-onion (CNO) electrode candidate for next-generation wearable energy storage devices.