A simple but efficient Li-doping approach for enhancing supercapacitor performance of the BiFeO₃ perovskite...

The capacitive energy storage mechanism offers quick charging, an extended life span, and, far, higher power density compared to batteries. This study presents a simple and efficient lithium (Li)-doping approach for enhancing electrochemical energy storage properties of perovskite-type bismuth ferrite (BiFeO₃) i.e. Bi_1-LiFeO₃ (BLFs), where x = 0, 0.05, 0.10, 0.15, and 0.20. An addition of the Li results in a significant decrease in the crystallite size of the BiFeO₃ from 67 nm to 26 nm, and, in addition to the surface morphology, the Bi/Fe ratio is changed. Electrochemical tests, performed in 6.0 M KOH electrolyte solutions in a half-cell system, have confirmed a significant increase in the specific capacitance (SC) and specific capacity values. After Li-doping, at a current density of 5 A g^-1, the SC of the pristine BLF electrode increases to 807.5 from 175.5 F g^-1 (specific capacity (Q) = 21.4-100.94 mA h g^-1) for the x = 0.10 Li-doped BLF electrode. The as-manufactured BLF-C//Bi₂S₃ asymmetric supercapacitor device, wherein Bi₂S₃ acts as a negative electrode and BLF-C as a positive electrode, in addition to an energy density of 48.65 W h kg^-1 and a power density of 750 W kg^-1, delivers an outstanding 155.6 F g^-1 SC (Q = 64.8 mA h g^-1) at a current density of 5 A g^-1. The 'CNED' screen, consisting of nearly 42 bright LEDs, is ignited at full brightness by connecting a twin-cell (BLF-C//Bi₂S₃) assembly. Even after 5000 redox cycles, the as-designed BLF-C//Bi₂S₃ asymmetric supercapacitor demonstrates an exceptional 92.67% cycling stability, suggesting the importance of an adopted Li-doping strategy for obtaining an enhanced energy storage performance in energy storage devices.