Chemically grown bismuth-oxy-iodide (BiOI/Bi9I2) nanostructure for high performance battery-type supercapacitor electrodes

Abstract

A dual phase bismuth oxyiodide (BiOI/Bi₉I₂) nanostructure battery type supercapacitor electrode is synthesized using chemical bath deposition (CBD) and the capacitance and energy/power density (ED/PD) reported. The supercapacitor electrode BiOI/Bi₉I₂ exhibited a specific capacitance of 515.5 F g⁻¹ (capacity value 143 mA h g⁻¹) at a current density of 2 A g⁻¹, with 80% of the original capacitance retained, even at a high current density of 4 A g⁻¹ over 5000 cycles. A pouch-type symmetric supercapacitor (PSS) device was created, based on BiOI/Bi₉I₂//BiOI/Bi₉I₂ electrodes (acting as anode and cathode electrodes) with 6 M KOH as the aqueous electrolyte and with an extended voltage up to 1.5 V. The ED value was 38.2 W h kg⁻¹ at a current density of 2 A g⁻¹, and the PD was 2280.4 W·kg⁻¹. Three PSS type BiOI/Bi₉I₂//BiOI/Bi₉I₂ devices were connected in series and used to illuminate a red LED for 20 min with full brightness, confirming potential use as an energy storage device. The above summarized results indicate that BiOI/Bi₉I₂//BiOI/Bi₉I₂ could be a potential electrode for battery type supercapacitor applications.