Solid-state, high-performance supercapacitor using graphene nanoribbons embedded with zinc manganite

Abstract

The fabrication of flexible supercapacitor involves the challenging task of preparing flexible electrodes with a large capacitance and robust mechanical strength. We report here the formulation of a high-performance solid-state flexible supercapacitor using graphene nanoribbons embedded with zinc manganite (ZnMn₂O₄/GNR) as the electrode and a gel polymer membrane as the electrolyte. The in situ availability of the graphene oxide nanoribbons led to the uniform dispersion of ZnMn₂O₄ nanospheres (about 7 nm), resulting in enhanced transport of the electrolyte ions. The fabricated ZnMn₂O₄/GNR∥ZnMn₂O₄/GNR supercapacitor was optimized with a maximum operating cell potential of 2.7 V. It delivered an energy density of about 37 W h kg⁻¹ and had a power density of about 30 kW kg⁻¹ at 1.25 A g⁻¹ with good cycling stability over 4000 cycles. The high diffusion coefficient and short relaxation time of 0.34 μs (at 75 °C) are indicators of its high performance and stability at increased temperature. The superior flexibility and durability of the supercapacitor cell are evidence of their performance stability over consecutive galvanostatic charge/discharge cycles under harsh conditions.