Employing Redox-Active Additives for Enhanced Charge Polarization and Twofold Higher Energy Density in Supercapacitor

Remarkable improvement in the polarization and charge transport at the solid-solid electrode-electrolyte interface due to the incorporation of a redox-active additive sodium molybdate (Na2MoO4) is demonstrated. The presence of the electrochemically active oxide center along with Na+ facilitates the hopping-based charge transport of the ionic liquid leading to higher ionic conductivity and a twofold increase in specific capacitance (0.009 to 0.018 F cm(-2)). This drives a 200% increase in the energy density (0.76-1.7 mu W h cm(-2)) and a 2.5 times improvement in the rate capability (10 000 mV s(-1)) of the solid-state supercapacitor. Importantly, the power density, non-Faradic nature, and cyclability remain unaltered, resulting in performance exceeding several solid-state and liquid electrolyte-based supercapacitors. Thus, the results established here through the use of redox-active additive establish the robustness of the approach and practicality of the resulting device besides providing transformative opportunities in tuning the performance of solid-state devices.