Tailored Co₃O₄/MnO₂ heterostructure via sequential ionic layering for high performance supercapacitor applications

Energy storage technology is facing the challenge of fabrication of low-cost supercapacitors with high specific energy without compromising its specific power and stability. The present work deals with the cost-effective and simple strategy towards the formation of Co₃O₄/MnO₂ core/shell electrodes to get rid of the aforementioned challenges. Herein, an easiest successive ionic layer adsorption and reaction (SILAR) method is employed to obtain hexagonal Co₃O₄ nanoplates which then coated with the state of art MnO₂ nanosheets forming highly porous core/shell electrode. Due to synergistic effect between Co₃O₄ and MnO₂, the Co₃O₄/MnO₂ core/shell electrode showed an improved specific capacitance of 744 F g⁻¹ and rate capability of 45 % for 5-fold increase in the current density. Moreover, it exhibited a capacitive retention of 85.3 % after 10,000 charge-discharge cycles at 10 A g⁻¹ which can be attributed to the vertically aligned Co₃O₄ nanoplates as backbone to the MnO₂ shell material. Furthermore, all-solid-state supercapacitor is fabricated between Co₃O₄/MnO₂//reduced graphene oxide using KOH-polyvinyl alcohol polymer based gel electrolyte. It delivered a maximum specific energy and specific power of 46.57 Wh kg⁻¹ and 2794 kW kg⁻¹, respectively. Finally, as-fabricated device performance is demonstrated through the discharge of 50 light emitting diodes (LEDs).