Sponge-Supported Low-Temperature Chemical Synthesis of the Hybrid Bi₂O₃@Ppy Electrode Material for Energy-Storage Devices

Most of the electrode materials used in energy-storage devices are either framed or deposited onto a conductive substrate. In the present work, the stretchable, foldable, and flexible commercial sponge, envisaged for cleaning in daily life, has been converted to a conducting material with the help of polypyrrole (PPy). The bismuth oxide (Bi2O3) electrode material of wool ball-like morphology is synthesized over pre-deposited PPy as a hybrid Bi2O3@PPy electrode using successive ionic layer adsorption and reaction method. Due to the special wool ball-like morphology of Bi2O3 and the porous structure of the PPy@sponge, more active sites with the shortest diffusion pathways for easy and fast electron-ion transportation are dominant. At a current density of 2 A g–1, the hybrid Bi2O3@PPy electrochemical supercapacitor (SC) exhibits a specific capacitance of 471.2 F g–1, and, even at a high current density of 10 A g–1, nearly 88% of the original capacitance has been retained over 5 K redox cycles. A pencil-type asymmetric supercapacitor designed using Bi2O3@PPy//graphite rod electrodes has delivered energy densities of 12 Wh kg–1 and 1363.6 W kg–1 of power density by consuming a 1.2 V voltage window in 3.0 M KOH aqueous electrolyte solution, and an excellent 70% cycling stability at a higher current density of 10 A g–1 is maintained. Two asymmetric supercapacitor devices connected in series can shine a red light-emitting diode with full brightness for 2 min, suggesting the energy storage efficacy of Bi2O3@PPy on the nonconductive substrate.