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 Fe 2+ storage during charge–discharge is a major challenge. Herein, V 2 O 5 porous microspheres (V 2 O 5 –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 V 2 O 5 –PMS cathode. The cyclic voltammetry measurements suggests a high diffusion coefficient of Fe 2+ ions in the redox process during charge–discharge. The V 2 O 5 –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.