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

Abstract

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−xLi_xFeO₃ (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.