GQD-Assisted MnO₆ Octahedra Engineering in CuMnO 2 for High Performance Coin-Cell Supercapacitor

Abstract

The growing demand for sustainable energy solutions has accelerated research into advanced supercapacitive electrode materials. This study explores the role of Graphene quantum dot (GQD) incorporation within CuMnO 2 in tailoring morphology and energy storage performances. Here, different degrees of MnO 6 octahedron distortion in CuMnO 2 nanostructure is achieved depending upon GQD concentration during hydrothermal reaction.Due to d-band centre modification and charge redistribution, optimally tuned CuMnO 2 /GQD nanostructure exhibits 213% increase in specific capacitance (~ 771.0 F g⁻¹ at 7.0 A g⁻¹) compared to the pristine counterpart in 3.0 M KOH. The fabricated full symmetric aqueous coin cell supercapacitor shows specific capacitance ~ 145.0 F g⁻¹ at 1.0 A g⁻¹, energy density of 34.2 Wh kg -1 at power density of 650 W kg -1 . We have confirmed repeatability of charging / discharging process over 5000 cycles of operation with 67% capacitance retention and 98% Coulombic efficiency. Whereas, aqueous asymmetric coin-cell supercapacitor with activated carbon anode, exhibits robust performance with high specific capacitance (~ 147.0 F g⁻¹ at 2.0 A g⁻¹), energy (~ 40 Wh kg -1 ) and power (~ 1398 W kg -1 ) densities. It also maintains ~71% capacity and 100% Coulombic efficiency after 5000 cycles. Real-world applicability is demonstrated by operating commercial LEDs, highlighting its potential as a high-performance electrode material for pseudocapacitive energy storage systems.