Low-Cost Aqueous Rechargeable Iron-Ion Battery in Ambient Conditions Using C3N4-Based Cathode

Lithium-ion batteries (LIBs) are extensively explored due to their higher gravimetric/volumetric capacity and energy density. However, constraints such as higher lithium cost limited lithium resources, and associated toxic, explosive, and highly reactive characteristics with water compel to hunt for alternative rechargeable batteries as efficient electrical energy storage systems. Iron, the second most abundant material with non-toxic characteristics and relatively lower cost, makes it an attractive system for rechargeable iron-ion batteries (RIIBs) with the possibility of an alternative to the LIBs for next-generation energy storage devices without any adverse effects or environmental impacts. However, the large size and slow diffusion are the materials’ issues that must be addressed. Here, RIIBs are fabricated under ambient conditions using mild steel as an anode for an iron source and graphitic carbon nitride as a cathode material. g-C3N4 material is synthesized via the thermal polymerization of melamine precursor and an aqueous electrolyte, including ferrous sulfate heptahydrate-based salts. Cyclic voltammetry was investigated to check the redox reaction at various scan rates. The galvanostatic charge–discharge (GCD) characteristics are measured at different current densities, showing a capacity of ~135 mAh g−1 at 1 A g−1, and a lower density of 0.5 A/g shows a higher gravimetric capacity of ~180 mAh/g. Its exhibits 50% capacity retention in 50 cycles at 1 A/g. The performance degradation was investigated using impedance analysis between the cycling and the post-mortem of the anode and cathode using the SEM-EDAX analysis after 150 GCD cycles.