Na2FePO4F Fluorophosphate as Positive Insertion Material for Aqueous Sodium-Ion Batteries

Exploring stable and economic cathodes for aqueous sodium-ion batteries, we have investigated iron-based fluorophosphate (Na2FePO4F) as a compound for applications in aqueous battery systems. Solution combustion synthesized Na2FePO4F is found to act as an efficient cathode for aqueous Na-ion batteries delivering a reversible capacity over 85 mAh g(-1) (at a rate of 1 mA cm(-2)) with excellent rate kinetics. Further, this layered Na2FePO4F has been successfully implemented to design a full aqueous cell with NASICON-type NaTi2(PO4)(3) as anode, delivering a reversible capacity of 90 mAh g(-1). In conclusion, Na2FePO4F is proposed as a potential cathode material for aqueous Na-ion batteries.