Iron-based perovskites-reduced graphene oxide as possible cathode materials for rechargeable iron-ion battery

Highlights: • AFeO₃-based perovskite/graphene composite was prepared using microwave-assisted method. • C_s in the order: Sr₂Fe₂O₅> LaFeO₃> SmFeO₃> NdFeO₃; due to differences in A-atom and Fe%. • C_s was enhanced by the addition of K₃[Fe(CN)₆] to KOH electrolyte the value is 675.1 C.g⁻¹. • AFeO₃ are crystalline; particle sizes are 5.7 (SmFeO₃), 4.4 (NdFeO₃) and 5.3 (Sr₂Fe₂O₅) nm. -- Abstract: In this manuscript, A-Fe-based perovskites (A = Sm, Nd, La and Sr)/RGO (AFOG) are reported for the first time as good cathode material candidates for post-lithium ion battery, namely rechargeable iron ion battery, Ni-Fe battery or super iron battery. AFOG materials are successfully prepared by the microwave-assisted graphene oxide (GO) method. Highly crystalline perovskites of less than 10 nm in diameter were successfully prepared without the need of any calcination step at elevated temperatures. The specific capacities of the resulting AFOG nanostructures were studied at relatively high charging/discharging rates in 1.0 M KOH electrolyte to test their high discharging rate capabilities. It was found that SrFOG provides the highest specific capacity due to the differences in its structure compared to the other AFOG nanocomposites. Upon the addition of 0.3 M K₃[Fe(CN)₆] to the 1.0 M KOH electrolyte, the specific capacities of AFOG have been greatly improved. A superior enhancement in the specific capacity was achieved with SrFOG that showed 187.5 mA·h·g⁻¹ in 0.3 M K₃[Fe(CN)₆]/1.0 M KOH compared to 19.6 mA·h·g⁻¹ in 1.0 M KOH at a scan-rate of 2 mV·s⁻¹. Moreover, SrFOG's specific capacity in 1.0 M KOH-containing ferricyanide showed 58-fold increase at a very high specific current of 10 A·g⁻¹ compared to its value in the ferricyanide-free KOH solution; ca. 97 mAh·g⁻¹ and 1.7 mA·h·g⁻¹, respectively.