Boosting Iron‐Ion Battery Performance with Porous Carbon Aerogel as High‐Rate Charge/Discharge Cathode

Rechargeable Iron‐ion batteries (IIBs) are emerging as a sustainable alternative to conventional rechargeable batteries; however, their cathode development is hindered by sluggish Fe‐ion diffusion, limited conductivity, and interfacial instability. Addressing these challenges requires designing cathode materials with high conductivity, large surface area, and stable electrochemical interfaces. This work explores carbon aerogel (CA)‐based cathodes to overcome these limitations and enhance Fe‐ion storage performance. Highly porous CA, used as the cathode material, is synthesized using the sol–gel process and confirmed using transmission electron microscopy, field emission scanning electron microscopy, X‐ray diffraction, and Brunauer–Emmett‐Teller measurements. Detailed cyclic voltammetry is investigated at different scan rates to understand the characteristics of the Fe‐ion storage in CA hosts during cycling. The galvanostatic charging–discharging (GCD) is determined at various current densities, showing a high discharge capacity of ≈150 mAh g −1 and ≈45 mAh g −1 at 35 mA g −1 and 1000 mA g −1 discharge current densities, respectively. The capacity retention is more than ≈60%, with more than 85% Coulombic efficiency (CE) after 750 cycles at 1000 mA g −1 , and fast charge–discharge characteristics of ≈18C rate. The galvanostatic intermittent titration technique (GITT) measurements are also performed to check the diffusion characteristics of the Fe‐ion during charging and discharging. A digital clock and 5V light‐emitting diode are connected to CA‐based Fe‐ion coin cells to demonstrate the potential of IIBs. A detailed electrochemical impedance spectroscopy and postmortem measurements before and after the GCD cycling suggest a slight degradation of electrochemical performance, which is attributed to the oxidation of the anode during cycling.