Quasi-Solid State and Hybrid Zinc Ion Photo-Supercapacitors Based on Manganese Oxide Nanostructures

The integrated devices, utilizing manganese oxide nanostructures in two different configurations, a quasi-solid state photo-supercapacitor, and an aqueous zinc ion hybrid photo-supercapacitor, were investigated for the direct conversion and storage of solar energy. The maximum specific capacitance of the quasi-solid state photo-supercapacitor devices in the dark was 23.8 F g(-1) at a 0.005 V s(-1) scan rate, increasing by 20.2% to reach 28.6 F g(-1) under AM1.5 illumination. A 55.5% increment in specific capacitance upon illumination was obtained for a quasi-solid state photo-supercapacitor at a 0.2 Vs(-1) scan rate. The zinc ion hybrid photo-supercapacitor device presented better performance compared to the quasi-solid state device. The highest specific capacitance of 140 Fg(-1) has been observed for the zinc ion hybrid photo-supercapacitor device charged to 1.5 V at 1.4 A g(-1) current density. The zinc ion hybrid photo-supercapacitor device operating at 2 V operating voltage under AM1.5 illumination has a record performance with 80 Whkg(-1) energy density and 7 kW kg(-1) power density. Both devices showed excellent stability at 100% capacitance retention at 170,000 and 10,000 galvanostatic charge-discharge cycles, respectively. The high stability, energy, and power densities obtained in this study indicate that both devices have great potential in next-generation energy applications.