Effect of Se on α -Bi 2 O 3 microspheres as a negative electrode in an asymmetric aqueous supercapacitor

Abstract Electrochemical supercapacitors are an indispensable energy source for managing surging energy consumption worldwide, owing to their ability to deliver high power density and rapid charge-discharge cycles. Bismuth-centric materials exhibit unprecedented specific capacities and high cyclic stability, making them potential candidates for supercapacitor devices. In pursuit of applications in supercapacitors, α -Bi 2 O 3, following Se@Bi 2 O 3 , was synthesized for various Se concentrations in Bi 2 O 3 . It was observed that Se/Bi 2 O 3 at 0.25 wt.% showed a high specific capacity of 306 C g −1 at 0.25 A g −1 . Furthermore, an asymmetric hybrid cell was devised using activated carbon as the positive electrode and Se@Bi 2 O 3 as the negative electrode in a 1 M Li 2 SO 4 electrolyte. The hybrid cell furnished a high specific capacity of 77.8 C g −1 at 0.25 A g −1 (for the total mass of the electrodes) and a specific energy of 17.33 Wh Kg −1 at a specific density of 401.56 W Kg −1 . The cell exhibits a maximum specific power of 8.8 kW kg −1 , a substantial current rate, and an energy density of 1.27 Wh Kg −1 . The cyclic stability of the fabricated hybrid capacitor was evaluated for AC/Se –0.25 @Bi 2 O 3 over 10 000 cycles, demonstrating an enhanced Coulombic efficiency >95% at 2 A g −1 . Thus, a range of Se dopant concentrations in α -Bi 2 O 3 was prepared for analysis, and AC/Se –0.25 @Bi 2 O 3 exhibited exceptional electrochemical efficiency across all aspects. We perform ab-initio density functional theory calculations using the Quantum Espresso platform to examine the substitutional doping of Se, where a single Selenium atom is replaced with Bi/O, to study the possible stable structural configurations.