A High-Performance and Fast-Charging Rechargeable Iron-Ion Battery Using V2O5 Porous Microspheres Cathode

Owing to iron's natural abundance, low cost, and affordability, nonaqueous rechargeable iron-ion (Fe-ion) batteries have the potential for alternative rechargeable energy-storage devices. However, developing cathodes with adequate superior Fe²⁺ storage during charge–discharge is a major challenge. Herein, V₂O₅ porous microspheres (V₂O₅–PMS) are synthesized as efficient cathodes due to their unique characteristics, including high surface area and large interlayer spacing, which provide high electrochemical performance and fast charge kinetics. The nonaqueous Fe-ion battery is fabricated under ambient conditions using mild steel as an anode and a V₂O₅–PMS cathode. The cyclic voltammetry measurements suggests a high diffusion coefficient of Fe²⁺ ions in the redox process during charge–discharge. The V₂O₅–PMS-based cathode shows ≈205 mAh g⁻¹ gravimetric capacity at 33 and ≈70 mAh g⁻¹ at 1 A g⁻¹ (≈15 C). It exhibits capacity retention of ≈70% in 600 cycles at a very high current rate of 3 A g⁻¹. The impedance spectroscopy measurements are carried out between the cell's cycling to understand the electrode–electrolyte interface resistance over cycling. The four CR-2032 coin cells are assembled in series to glow a white and red light-emitting diode to demonstrate its potential as an alternative energy-storage system.