Mg-substituted Prussian blue as a low-strain cathode material for aqueous Fe-ion batteries.

Aqueous Fe-ion batteries (FIBs) have gradually emerged in recent years due to their inherent merits. Herein, we constructed a Mg-substituted Prussian blue analogue (MgFeHCF) as cathode for FIBs, achieving higher capacity (96 mA h g -1 ) and better stability (70.9% capacity retention over 500 cycles). The Fe-ion storage mechanism was revealed using the in situ XRD technique and DFT calculations were employed to analyse the battery performance.